Liquid crystal display device

ABSTRACT

A liquid crystal display device includes: a vertical alignment liquid crystal layer; first and second substrates facing each other with the liquid crystal layer interposed; first and second electrodes arranged on the first and second substrates to face the liquid crystal layer; and at least one alignment film in contact with the liquid crystal layer. A pixel region includes a first liquid crystal domain in which liquid crystal molecules are tilted in a first direction around the center of a plane, and approximately at the middle of the thickness, of the liquid crystal layer responsive to a voltage applied. The first liquid crystal domain is close to at least a part of an edge of the first electrode. The part includes a first edge portion in which an azimuthal direction, perpendicular to the part and pointing toward the inside of the first electrode, defines an angle greater than 90 degrees to the first direction. The first or second substrate has an opaque member including a first opaque portion for selectively shielding at least a part of the first edge portion from incoming light.

This application is the U.S. national phase of International ApplicationNo. PCT/JP/2006/311640 filed 9 Jun. 2006 which designated the U.S. andclaims priority to JP 2005-169423 filed 9 Jun. 2005 and JP 2006-158140filed 7 Jun. 2006, the entire contents of each of which are herebyincorporated by reference.

TECHNICAL FIELD

The present invention relates to a liquid crystal display device andmore particularly relates to a liquid crystal display device with a wideviewing angle characteristic.

BACKGROUND ART

Recently, the display performances of liquid crystal displays (LCDs)have been improved to the point that more and more manufacturers adoptLCD panels as TV monitors, for example. The viewing angle characteristicof LCDs has been improved to a certain degree but not satisfactorily insome respects. Among other things, there is still a high demand forimprovement of the viewing angle characteristic of an LCD using avertical alignment liquid crystal layer (which is sometimes called a “VAmode LCD”).

A VA mode LCD, which is currently used for a TV set with a big screen,for example, adopts a multi-domain structure, in which multiple liquidcrystal domains are formed in a single pixel region, to improve theviewing angle characteristic. An MVA mode is often adopted as a methodof forming such a multi-domain structure. Specifically, according to theMVA mode, an alignment control structure is provided on one of the twosubstrates, which face each other with a vertical alignment liquidcrystal layer interposed between them, so as to contact with the liquidcrystal layer, thereby forming multiple domains with mutually differentalignment directions (i.e., tilt directions), the number of which istypically four. As the alignment control structure, a slit (as anopening) or a rib (as a projection structure) may be provided for anelectrode, thereby creating an anchoring force from both sides of theliquid crystal layer.

If a slit or a rib is adopted, however, the anchoring force will beapplied onto liquid crystal molecules non-uniformly within a pixelregion because the slit or rib has a linear structure unlike thesituation where the pretilt directions are defined by an alignment filmin a conventional TN mode LCD. As a result, the response speed may havea distribution unintentionally. In addition, since the transmittance oflight will decrease in the areas with the slits or ribs, the luminanceof the screen will decrease, too.

-   -   Patent Document No. 1: Japanese Patent Application Laid-Open        Publication No. 11-133429    -   Patent Document No. 2: Japanese Patent Application Laid-Open        Publication No. 11-352486

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

To avoid such a problem, the multi-domain structure is preferably formedby defining the pretilt directions with an alignment film for a VA modeLCD, too. Thus, the present inventors discovered and confirmed viaexperiments that a unique misalignment occurred in a VA mode LCD andaffected its display quality.

Even in a conventional LCD in which the multi-domain structure is formedusing an alignment film, a technique for providing an opaque portion forcutting the light that has been transmitted through an area withmisalignment to minimize the deterioration in display quality due to themisalignment is also known (see Patent Document No. 1, for example).

The conventional multi-domain structure is provided with such an opaqueportion to shield an area with an optical transmittance that is higherthan a predetermined value (i.e., an area that looks brighter whenviewed straight than an area where liquid crystal molecules are alignednormally) due to a misalignment such as a reverse tilt in a TN mode LCD,for example. However, the present inventors discovered that the displayquality of a VA mode LCD could not be improved sufficiently just byshielding such an area that looked brighter when viewed straight than anarea where liquid crystal molecules were aligned normally.

In order to overcome the problems described above, the present inventionhas an object of providing a VA mode liquid crystal display device withexcellent display quality.

Means for Solving the Problems

A liquid crystal display device according to the present inventionincludes: a vertical alignment liquid crystal layer; a first substrateand a second substrate, which face each other with the liquid crystallayer interposed between them; a first electrode, which is arranged onthe first substrate so as to face the liquid crystal layer; a secondelectrode, which is arranged on the second substrate so as to face theliquid crystal layer; and at least one alignment film, which is arrangedin contact with the liquid crystal layer. A pixel region includes atleast one liquid crystal domain that produces a dark area, which looksdarker than a gray scale level being presented for a viewer located infront of the device, inside of, and substantially parallel to, an edgeportion of the first electrode. Either the first substrate or the secondsubstrate has an opaque member that includes at least one opaque portionfor selectively shielding at least a portion of the dark area fromincoming light.

Another liquid crystal display device according to the present inventionincludes: a vertical alignment liquid crystal layer; a first substrateand a second substrate, which face each other with the liquid crystallayer interposed between them; a first electrode, which is arranged onthe first substrate so as to face the liquid crystal layer; a secondelectrode, which is arranged on the second substrate so as to face theliquid crystal layer; and at least one alignment film, which is arrangedin contact with the liquid crystal layer. A pixel region includes afirst liquid crystal domain in which liquid crystal molecules are tiltedin a predetermined first direction around the center of a plane, andapproximately at the middle of the thickness, of the liquid crystallayer in response to a voltage applied. The first liquid crystal domainis located close to at least a part of an edge of the first electrode.The part includes a first edge portion in which an azimuthal directionthat is perpendicular to the part and that points toward the inside ofthe first electrode defines an angle greater than 90 degrees withrespect to the first direction. Either the first substrate or the secondsubstrate has an opaque member that includes a first opaque portion forselectively shielding at least a part of the first edge portion fromincoming light.

In one embodiment, the pixel region further includes second, third andfourth liquid crystal domains in which liquid crystal molecules aretilted in second, third and fourth directions, respectively, around thecenter of the plane, and approximately at the middle of the thickness,of the liquid crystal layer in response to the voltage applied. Thefirst, second, third and fourth directions are defined such that anangle formed between any two of the four directions is approximatelyequal to an integral multiple of 90 degrees. The second liquid crystaldomain is located close to at least a part of another edge of the firstelectrode, and the part includes a second edge portion in which anazimuthal direction that is perpendicular to the part and that pointstoward the inside of the first electrode defines an angle greater than90 degrees with respect to the second direction. The third liquidcrystal domain is located close to at least a part of still another edgeof the first electrode, and the part includes a third edge portion inwhich an azimuthal direction that is perpendicular to the part and thatpoints toward the inside of the first electrode defines an angle greaterthan 90 degrees with respect to the third direction. The fourth liquidcrystal domain is located close to at least a part of yet another edgeof the first electrode, and the part includes a fourth edge portion inwhich an azimuthal direction that is perpendicular to the part and thatpoints toward the inside of the first electrode defines an angle greaterthan 90 degrees with respect to the fourth direction. The opaque memberfurther includes second, third and fourth opaque portions forselectively shielding at least a part of the second, third and fourthedge portions, respectively, from incoming light.

In one embodiment, the first, second, third and fourth liquid crystaldomains are arranged such that the tilt directions of any two adjacentones of the liquid crystal domains define an angle of approximately 90degrees between them.

In one embodiment, if the horizontal direction of a display screen hasan azimuthal angle of zero degrees, the first, second, third and fourthdirections are an approximately 225 degree direction, an approximately315 degree direction, an approximately 45 degree direction and anapproximately 135 degree direction, respectively. The first and thirdedge portions are parallel to a vertical direction and the second andfourth edge portions are parallel to the horizontal direction.

In one embodiment, if the horizontal direction of a display screen hasan azimuthal angle of zero degrees, the first, second, third and fourthdirections are an approximately 225 degree direction, an approximately315 degree direction, an approximately 45 degree direction and anapproximately 135 degree direction, respectively. The first and thirdedge portions are parallel to the horizontal direction and the secondand fourth edge portions are parallel to a vertical direction.

In one embodiment, if the horizontal direction of a display screen hasan azimuthal angle of zero degrees, the first, second, third and fourthdirections are an approximately 225 degree direction, an approximately315 degree direction, an approximately 45 degree direction and anapproximately 135 degree direction, respectively. Each of the first,second, third and fourth edge portions includes a first part that isparallel to the horizontal direction and a second part that is parallelto a vertical direction.

In one embodiment, the pixel region further includes second, third andfourth liquid crystal domains in which liquid crystal molecules aretilted in second, third and fourth directions, respectively, around thecenter of the plane, and approximately at the middle of the thickness,of the liquid crystal layer in response to the voltage applied. Thefirst, second, third and fourth directions are defined such that anangle formed between any two of the four directions is approximatelyequal to an integral multiple of 90 degrees. The first and seconddirections form an angle of approximately 180 degrees between them. Thesecond liquid crystal domain is located close to at least a part ofanother edge of the first electrode, and the part includes a second edgeportion in which an azimuthal direction that is perpendicular to thepart and that points toward the inside of the first electrode defines anangle greater than 90 degrees with respect to the second direction. Eachof the first and second edge portions includes a first part that isparallel to the horizontal direction and a second part that is parallelto a vertical direction. And the opaque member further includes a secondopaque portion for selectively shielding at least a part of the secondedge portion from incoming light.

In one embodiment, if the horizontal direction on the display screen hasan azimuthal angle of zero degrees, the first direction is either anapproximately 135 degree direction or an approximately 225 degreedirection.

In one embodiment, if the horizontal direction of a display screen hasan azimuthal angle of zero degrees, the first, second, third and fourthdirections are an approximately 90 degree direction, an approximately180 degree direction, an approximately 0 degree direction and anapproximately 270 degree direction, respectively. The first and fourthedge portions are parallel to the horizontal direction and the secondand third edge portions are parallel to a vertical direction.

In one embodiment, if the horizontal direction of a display screen hasan azimuthal angle of zero degrees, the first, second, third and fourthdirections are an approximately 225 degree direction, an approximately315 degree direction, an approximately 45 degree direction and anapproximately 135 degree direction, respectively. The first, second,third and fourth edge portions are all parallel to a vertical direction.

In one embodiment, the opaque member includes a central opaque portionfor selectively shielding at least a portion of a boundary area of eachof the first, second, third and fourth liquid crystal domains, which isadjacent to another one of the liquid crystal domains, from incominglight.

In one embodiment, the opaque member includes another opaque portion forshielding an intersection between a boundary area of each of the first,second, third and fourth liquid crystal domains, which is adjacent toanother one of the liquid crystal domains, and one of the first, second,third and fourth edge portions from incoming light.

In one embodiment, the first substrate further includes a TFT, a gatebus line, a source bus line, a drain extension line, and a storagecapacitor line. One of the first, second, third, fourth, central andanother opaque portions is defined by at least a portion of at least oneline selected from the group consisting of the gate bus line, the sourcebus line, the drain extension line, and the storage capacitor line.

In one embodiment, the at least one line has a portion that is bent orbroadened in a direction that crosses its length direction, and the atleast the portion of the at least one line includes at least a part ofthe bent or broadened portion.

In one embodiment, the second substrate further includes a black matrixlayer, and one of the first, second, third, fourth, central and anotheropaque portions is defined by a portion of the black matrix layer.

In one embodiment, the liquid crystal display device further includestwo polarizers, which are arranged so as to face each other with theliquid crystal layer interposed between them and to have theirtransmission axes crossed at right angles. The first, second, third andfourth directions define an angle of approximately 45 degrees withrespect to the transmission axes of the two polarizers.

In one embodiment, the vertical alignment liquid crystal layer includesa liquid crystal material with negative dielectric anisotropy. The atleast one alignment film includes two alignment films that are arrangedso as to sandwich the liquid crystal layer between them. Respectivepretilt directions defined by the two alignment films are different fromeach other by approximately 90 degrees.

In one embodiment, the at least one alignment film includes twoalignment films that are arranged so as to sandwich the liquid crystallayer between them. Respective pretilt angles defined by the twoalignment films are substantially equal to each other.

In one embodiment, the at least one alignment film is a photo-alignmentfilm.

Still another liquid crystal display device according to the presentinvention includes: a vertical alignment liquid crystal layer; a firstsubstrate and a second substrate, which face each other with the liquidcrystal layer interposed between them; a first electrode, which isarranged on the first substrate so as to face the liquid crystal layer;a second electrode, which is arranged on the second substrate so as toface the liquid crystal layer; and at least one alignment film, which isarranged in contact with the liquid crystal layer. A pixel regionincludes first, second, third and fourth liquid crystal domains in whichliquid crystal molecules are tilted in first, second, third and fourthdirections, respectively, around the center of a plane, andapproximately at the middle of the thickness, of the liquid crystallayer in response to a voltage applied. The first, second, third andfourth directions are defined such that an angle formed between any twoof the four directions is approximately equal to an integral multiple of90 degrees. Each of the first, second, third and fourth liquid crystaldomains is adjacent to another one of the liquid crystal domains. Anopaque member includes a central opaque portion for selectivelyshielding at least a portion of a boundary area of each of the first,second, third and fourth liquid crystal domains, which is adjacent toanother one of the liquid crystal domains, from incoming light.

In one embodiment, the first liquid crystal domain is located close toat least a part of an edge of the first electrode, and the part includesa first edge portion in which an azimuthal direction that isperpendicular to the part and that points toward the inside of the firstelectrode defines an angle greater than 90 degrees with respect to thefirst direction. The second liquid crystal domain is located close to atleast a part of another edge of the first electrode, and the partincludes a second edge portion in which an azimuthal direction that isperpendicular to the part and that points toward the inside of the firstelectrode defines an angle greater than 90 degrees with respect to thesecond direction. The third liquid crystal domain is located close to atleast a part of still another edge of the first electrode, and the partincludes a third edge portion in which an azimuthal direction that isperpendicular to the part and that points toward the inside of the firstelectrode defines an angle greater than 90 degrees with respect to thethird direction. The fourth liquid crystal domain is located close to atleast a part of yet another edge of the first electrode, and the partincludes a fourth edge portion in which an azimuthal direction that isperpendicular to the part and that points toward the inside of the firstelectrode defines an angle greater than 90 degrees with respect to thefourth direction.

In one embodiment, the first, second, third and fourth liquid crystaldomains are arranged in two rows and two columns so as to define amatrix pattern.

In one embodiment, the first, second, third and fourth liquid crystaldomains are arranged in line in a predetermined direction.

In one embodiment, the first substrate further includes a TFT, a gatebus line, a source bus line, a drain extension line, and a storagecapacitor line, and the central opaque portion is defined by at least aportion of at least one line selected from the group consisting of thegate bus line, the source bus line, the drain extension line, and thestorage capacitor line.

In one embodiment, the at least one line has a portion that is bent orbroadened in a direction that crosses its length direction, and the atleast the portion of the at least one line includes at least a part ofthe bent or broadened portion.

In one embodiment, the second substrate further includes a black matrixlayer, and the central opaque portion is defined by a portion of theblack matrix layer.

In one embodiment, the liquid crystal display device further includestwo polarizers, which are arranged so as to face each other with theliquid crystal layer interposed between them and to have theirtransmission axes crossed at right angles. The first, second, third andfourth directions define an angle of approximately 45 degrees withrespect to the transmission axes of the two polarizers.

In one embodiment, the vertical alignment liquid crystal layer includesa liquid crystal material with negative dielectric anisotropy. The atleast one alignment film includes two alignment films that are arrangedso as to sandwich the liquid crystal layer between them. Respectivepretilt directions defined by the two alignment films are different fromeach other by approximately 90 degrees.

In one embodiment, the at least one alignment film includes twoalignment films that are arranged so as to sandwich the liquid crystallayer between them, and respective pretilt angles defined by the twoalignment films are substantially equal to each other.

In one embodiment, the at least one alignment film is a photo-alignmentfilm.

Yet another liquid crystal display device according to the presentinvention includes: a vertical alignment liquid crystal layer; a firstsubstrate and a second substrate, which face each other with the liquidcrystal layer interposed between them; a first electrode, which isarranged on the first substrate so as to face the liquid crystal layer;a second electrode, which is arranged on the second substrate so as toface the liquid crystal layer; and at least one alignment film, which isarranged in contact with the liquid crystal layer. A pixel regionincludes first, second, third and fourth liquid crystal domains in whichliquid crystal molecules are tilted in first, second, third and fourthdirections, respectively, around the center of a plane, andapproximately at the middle of the thickness, of the liquid crystallayer in response to a voltage applied. The first, second, third andfourth directions are defined such that an angle formed between any twoof the four directions is approximately equal to an integral multiple of90 degrees. The first liquid crystal domain is located close to at leasta part of an edge of the first electrode, and the part includes a firstedge portion in which an azimuthal direction that is perpendicular tothe part and that points toward the inside of the first electrodedefines an angle greater than 90 degrees with respect to the firstdirection. The second liquid crystal domain is located close to at leasta part of another edge of the first electrode, and the part includes asecond edge portion in which an azimuthal direction that isperpendicular to the part and that points toward the inside of the firstelectrode defines an angle greater than 90 degrees with respect to thesecond direction. The third liquid crystal domain is located close to atleast a part of still another edge of the first electrode, and the partincludes a third edge portion in which an azimuthal direction that isperpendicular to the part and that points toward the inside of the firstelectrode defines an angle greater than 90 degrees with respect to thethird direction. The fourth liquid crystal domain is located close to atleast a part of yet another edge of the first electrode, and the partincludes a fourth edge portion in which an azimuthal direction that isperpendicular to the part and that points toward the inside of the firstelectrode defines an angle greater than 90 degrees with respect to thefourth direction. Each of the first, second, third and fourth liquidcrystal domains is adjacent to another one of the liquid crystaldomains. Either the first substrate or the second substrate includes anopaque member, which includes an opaque portion for shielding anintersection between a boundary area of each of the first, second, thirdand fourth liquid crystal domains, which is adjacent to another one ofthe liquid crystal domains, and one of the first, second, third andfourth edge portions from incoming light.

In one embodiment, the first, second, third and fourth liquid crystaldomains are arranged such that the tilt directions of any two adjacentones of the liquid crystal domains define an angle of approximately 90degrees between them.

In one embodiment, if the horizontal direction of a display screen hasan azimuthal angle of zero degrees, the first, second, third and fourthdirections are an approximately 225 degree direction, an approximately315 degree direction, an approximately 45 degree direction and anapproximately 135 degree direction, respectively. The first and thirdedge portions are parallel to a vertical direction and the second andfourth edge portions are parallel to the horizontal direction.

In one embodiment, if the horizontal direction of a display screen hasan azimuthal angle of zero degrees, the first, second, third and fourthdirections are an approximately 225 degree direction, an approximately315 degree direction, an approximately 45 degree direction and anapproximately 135 degree direction, respectively. The first and thirdedge portions are parallel to the horizontal direction and the secondand fourth edge portions are parallel to a vertical direction.

In one embodiment, if the horizontal direction of a display screen hasan azimuthal angle of zero degrees, the first, second, third and fourthdirections are an approximately 90 degree direction, an approximately180 degree direction, an approximately 0 degree direction and anapproximately 270 degree direction, respectively. The first and fourthedge portions are parallel to the horizontal direction and the secondand third edge portions are parallel to a vertical direction.

In one embodiment, if the horizontal direction of a display screen hasan azimuthal angle of zero degrees, the first, second, third and fourthdirections are an approximately 225 degree direction, an approximately315 degree direction, an approximately 45 degree direction and anapproximately 135 degree direction, respectively. The first, second,third and fourth edge portions are all parallel to a vertical direction.

In one embodiment, the opaque portion is substantially triangular.

In one embodiment, an opaque member includes a central opaque portionfor selectively shielding at least a portion of a boundary area of eachof the first, second, third and fourth liquid crystal domains, which isadjacent to another one of the liquid crystal domains, from incominglight.

In one embodiment, the first substrate further includes a TFT, a gatebus line, a source bus line, a drain extension line, and a storagecapacitor line. Either the opaque portion or the central opaque portionis defined by at least a portion of at least one line selected from thegroup consisting of the gate bus line, the source bus line, the drainextension line, and the storage capacitor line.

In one embodiment, the second substrate further includes a black matrixlayer, and either the opaque portion or the central opaque portion isdefined by a portion of the black matrix layer.

In one embodiment, the liquid crystal display device further includestwo polarizers, which are arranged so as to face each other with theliquid crystal layer interposed between them and to have theirtransmission axes crossed at right angles. The first, second, third andfourth directions define an angle of approximately 45 degrees withrespect to the transmission axes of the two polarizers.

In one embodiment, the vertical alignment liquid crystal layer includesa liquid crystal material with negative dielectric anisotropy, and theat least one alignment film includes two alignment films that arearranged so as to sandwich the liquid crystal layer between them. Thepretilt direction defined by one of the two alignment films is differentfrom that defined by the other alignment film by approximately 90degrees.

In one embodiment, the at least one alignment film includes twoalignment films that are arranged so as to sandwich the liquid crystallayer between them, and respective pretilt angles defined by the twoalignment films are substantially equal to each other.

In one embodiment, the at least one alignment film is a photo-alignmentfilm.

EFFECTS OF THE INVENTION

According to the present invention, the display quality of a VA modeliquid crystal display device can be improved in terms of its viewingangle dependence, in particular. Also, according to the presentinvention, the display quality of a liquid crystal display device havinga multi-domain structure defined by an alignment film can be improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an exemplary pixel region with a multi-domainstructure in a VA mode liquid crystal display device according to thepresent invention.

FIGS. 2( a) and 2(b) illustrate exemplary pixel regions with amulti-domain structure in a VA mode liquid crystal display deviceaccording to the present invention.

FIGS. 3( a) and 3(b) illustrate other exemplary pixel regions with amulti-domain structure in a VA mode liquid crystal display deviceaccording to the present invention.

FIGS. 4( a) and 4(b) illustrate still other exemplary pixel regions witha multi-domain structure in a VA mode liquid crystal display deviceaccording to the present invention.

FIGS. 5( a) and 5(b) illustrate yet other exemplary pixel regions with amulti-domain structure in a VA mode liquid crystal display deviceaccording to the present invention.

FIG. 6 is a cross-sectional view of a pixel region of a VA mode liquidcrystal display device according to the present invention, showing theequipotential curve of an electric field created in the liquid crystallayer, the orientation directions of liquid crystal molecules in thelayer, and the transmittance thereof, which were figured out bysimulations.

FIG. 7 is a cross-sectional view of a pixel region of a VA mode liquidcrystal display device according to the present invention, showing theequipotential curve of an electric field created in the liquid crystallayer, the orientation directions of liquid crystal molecules in thelayer, and the transmittance thereof, which were figured out bysimulations.

FIG. 8 is a cross-sectional view of a pixel region of a VA mode liquidcrystal display device according to the present invention, showing theequipotential curve of an electric field created in the liquid crystallayer, the orientation directions of liquid crystal molecules in thelayer, and the transmittance thereof, which were figured out bysimulations.

FIG. 9 is a cross-sectional view of a pixel region of a VA mode liquidcrystal display device according to the present invention, showing theequipotential curve of an electric field created in the liquid crystallayer, the orientation directions of liquid crystal molecules in thelayer, and the transmittance thereof, which were figured out bysimulations.

FIG. 10 is graphs showing the distributions of transmission intensitiesin a situation where the pixel region shown in FIG. 2( a) is viewed fromthe direction defined by an azimuth angle of 45 degrees.

FIG. 11 is a schematic representation illustrating an exemplary pixelstructure for a liquid crystal display device according to the presentinvention.

FIG. 12 is a schematic representation illustrating another exemplarypixel structure for a liquid crystal display device according to thepresent invention.

FIG. 13 is a schematic representation illustrating still anotherexemplary pixel structure for a liquid crystal display device accordingto the present invention.

FIG. 14 is a schematic representation illustrating yet another exemplarypixel structure for a liquid crystal display device according to thepresent invention.

FIG. 15 is a cross-sectional view schematically illustrating the pixelstructure shown in FIG. 14.

FIG. 16 is a schematic representation illustrating yet another exemplarypixel structure for a liquid crystal display device according to thepresent invention.

FIG. 17 is a cross-sectional view schematically illustrating the pixelstructure shown in FIG. 16.

FIG. 18 is a schematic representation illustrating yet another exemplarypixel structure for a liquid crystal display device according to thepresent invention.

FIG. 19 is a schematic representation illustrating yet another exemplarypixel structure for a liquid crystal display device according to thepresent invention.

FIG. 20 is a schematic representation illustrating yet another exemplarypixel structure for a liquid crystal display device according to thepresent invention.

FIG. 21 is a schematic representation illustrating yet another exemplarypixel structure for a liquid crystal display device according to thepresent invention.

FIG. 22 is a schematic representation showing another area in whichmisalignment occurs in a pixel region with a multi-domain structure in aVA mode liquid crystal display device according to the presentinvention.

FIG. 23 is a schematic representation illustrating yet another exemplarypixel structure for a liquid crystal display device according to thepresent invention.

FIG. 24 is a schematic representation illustrating yet another exemplarypixel structure for a liquid crystal display device according to thepresent invention.

FIG. 25 is a schematic representation illustrating yet another exemplarypixel structure for a liquid crystal display device according to thepresent invention.

FIGS. 26( a) through 26(c) show how the viewing angle characteristicchanges with the central opaque portion in a situation where thephotomask has misaligned, wherein: FIG. 26( a) schematically illustratesa pixel with only a vertical opaque portion 21; FIG. 26( b)schematically illustrates a pixel with only a horizontal opaque portion22; and FIG. 26( c) schematically illustrates a pixel with no centralopaque portion at all.

FIGS. 27( a) and 27(b) show how the location of a domain line changesaccording to the pretilt angle, wherein: FIG. 27( a) schematicallyillustrates a pixel including a liquid crystal layer with a pretiltangle of 87.5 degrees; and FIG. 27( b) schematically illustrates a pixelincluding a liquid crystal layer with a pretilt angle of 89.0 degrees.

FIG. 28 is a graph showing how the transmittance (or luminance) changeswith the pretilt angle.

FIG. 29 is a graph showing how the contrast ratio changes with thepretilt angle.

DESCRIPTION OF REFERENCE NUMERALS

-   -   1 TFT substrate    -   1 a, 2 a transparent substrate    -   2 CF substrate    -   3 liquid crystal layer    -   3 a liquid crystal molecule    -   10 pixel region    -   11 pixel electrode    -   12 counter electrode    -   111 pixel electrode    -   111 a subpixel electrode    -   111E broadened portion of pixel electrode or subpixel electrode    -   112 gate bus line    -   113 CS bus line (storage capacitor line)    -   113E extended portion of CS bus line    -   114 source bus line    -   116, 116 a, 116 b TFT    -   117 drain extension line    -   117E extended portion of drain extension line    -   SD1 to SD4 edges of pixel electrode    -   EG1 to EG4 edge portions of pixel electrode    -   A to D liquid crystal domain    -   t1 to t4 tilt direction (reference alignment direction)    -   e1 to e4 azimuth direction that is perpendicular to edge of        pixel electrode and pointed inward in pixel electrode

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of a liquid crystal display device according tothe present invention will be described with reference to theaccompanying drawings. However, the present invention is in no waylimited to the following specific embodiments. According to the presentinvention, a liquid crystal display device, including a verticalalignment liquid crystal layer of which the pretilt direction iscontrolled by using at least one alignment film, has its display qualityimproved by providing an opaque film where misalignment occurs.

The display quality is affected to different degrees depending on wheremisalignment has occurred. That is why the type of misalignment to behidden behind an opaque portion also changes with the displayperformance required. In the following description, three types ofmisalignment to occur in three different locations in a pixel region(namely, an electrode edge portion, a central portion and anintersection portion) will be described separately. These threelocations may be shielded independently of each other. Two or more ofthese locations may be shielded in any arbitrary combination or all ofthem may be shielded, too.

As used herein, the “vertical alignment liquid crystal layer” means aliquid crystal layer in which the axis of liquid crystal molecules(which will be sometimes referred to herein as an “axis direction”)defines a tilt angle of approximately 85 degrees or more with respect tothe surface of a vertical alignment film. The liquid crystal moleculeshave negative dielectric anisotropy and are combined with polarizersthat are arranged as crossed Nicols to conduct a display operation innormally black mode. The alignment film may be provided for at least oneof the two substrates. However, to stabilize the alignment, each of thetwo substrates is preferably provided with an alignment film. In theembodiment to be described below, each of the two substrates is providedwith a vertical alignment film. Also, since every misalignment occurswithin the multi-domain structure except that occurring in an electrodeedge portion, a four-domain structure that realizes a particularly goodviewing angle characteristic will be described as an example. As usedherein, the “pixel” refers to a minimum unit for representing aparticular gray scale level on the screen, and corresponds to a unit forrepresenting each gray scale level of red (R), green (G) and blue (B) incolor display and is also called a “dot”. A combination of R, G and Bpixels forms a single color display pixel. The “pixel region” refers toa region of a liquid crystal display device that is allocated to asingle “pixel” on the screen. The “pretilt direction” is the orientationdirection of liquid crystal molecules to be controlled with an alignmentfilm and refers to an azimuthal direction on a display screen. Also, theangle formed by the liquid crystal molecules with respect to the surfaceof the alignment film in this case will be referred to herein as a“pretilt angle”. The pretilt direction will be defined by subjecting thealignment film to a rubbing treatment or a photo-alignment treatment. Bychanging the combinations of the pretilt directions of the two alignmentfilms that face each other with the liquid crystal layer interposedbetween them, the four-domain structure can be formed. The quadruplepixel region includes four liquid crystal domains (which will besometimes simply referred to herein as “domains”). Each of these liquidcrystal domains is characterized by the tilt direction of liquid crystalmolecules at the center of a plane of the liquid crystal layer, to whicha voltage is being applied, and at the middle of the thickness of theliquid crystal layer. Such a tilt direction will be sometimes referredto herein as a “reference alignment direction”. And this tilt direction(or reference alignment direction) will have an important effect on theviewing angle dependence of each domain. The tilt direction is also anazimuthal direction. The reference azimuthal direction is supposed to bethe horizontal direction on the screen and the azimuth angle is supposedto increase counterclockwise. For example, comparing the display screento a clock face, the three o'clock direction is supposed to have anazimuth angle of zero degrees and the angle is supposed to increasecounterclockwise. By defining the tilt directions of the four liquidcrystal domains such that an angle formed between any two of the fourdirections is approximately equal to an integral multiple of 90 degrees(e.g., as the twelve o'clock direction, the nine o'clock direction, thesix o'clock direction and the three o'clock direction, respectively),highly uniform viewing angle characteristic and good display quality arerealized. To increase the uniformity of the viewing anglecharacteristic, the areas of those four liquid crystal domains in thepixel region are preferably equalized with each other. Specifically, thedifference between the area of the largest one of the four liquidcrystal domains and that of the smallest one of the four is preferablyno greater than 25% of the largest area.

The vertical alignment liquid crystal layer of the embodiment to bedescribed below includes a nematic liquid crystal material with negativedielectric anisotropy. The pretilt directions defined by the twoalignment films that sandwich the liquid crystal layer between them aredifferent from each other by approximately 90 degrees. The tilt angle(i.e., the reference alignment direction) is defined as an intermediatedirection between these two pretilt directions. No chiral agent is addedto the liquid crystal layer. And when a voltage is applied to the liquidcrystal layer, the liquid crystal molecules located near the alignmentfilms will have a twisted alignment under the anchoring force of thealignment films. If necessary, a chiral agent may be added to the liquidcrystal layer. By using such a pair of vertical alignment films definingtwo pretilt directions (alignment treatment directions) that areperpendicular to each other, the VA mode in which the liquid crystalmolecules have a twisted alignment is sometimes called a verticalalignment twisted nematic (VATN) mode (see Patent Document No. 2, forexample).

In the VATN mode, the pretilt angles defined by the two alignment filmsare preferably substantially equal to each other as disclosed by theapplicant of the present application in Japanese Patent Application No.2005-141846. By using such a pair of alignment films defining pretiltangles that are approximately equal to each other, the display luminancecan be increased. Particularly when the difference between the pretiltangles defined by the two alignment films is within one degree, the tiltdirection (i.e., the reference alignment direction) of liquid crystalmolecules, located approximately at the middle of the thickness of theliquid crystal layer, can be controlled with good stability and thedisplay luminance can be increased. This is probably because if thedifference between the pretilt angles were more than one degree, thenthe tilt direction would vary noticeably from one location to another inthe liquid crystal layer and the transmittance would vary significantlyas a result (i.e., some area would have a lower transmittance than adesired one).

According to known methods, the pretilt direction of liquid crystalmolecules may be defined by alignment films by subjecting the alignmentfilms to a rubbing treatment or a photo-alignment treatment, by forminga microstructure on an undercoat film for each alignment film andtransferring the pattern of the microstructure onto the surface of thealignment film, or by evaporating obliquely an inorganic material suchas SiO on an alignment film to define a microstructure thereon.Considering its mass productivity, either the rubbing treatment or thephoto-alignment treatment is preferred. Among other things, thephoto-alignment treatment is particularly to increase the yield becausethat treatment is a non-contact method and generates no staticelectricity due to friction unlike the rubbing treatment. Also, asdescribed in Japanese Patent Application No. 2005-141846 mentionedabove, by using a photo-alignment film including a photosensitive group,the variation in pretilt angle can be reduced to one degree or less. Thephoto-alignment film preferably includes at least one photosensitivegroup selected from the group consisting of a 4-chalcone group, a4′-chalcone group, a coumarin group, and a cinnamoyl group to name afew.

The embodiment to be described below is a TFT LCD as a typical example.However, the present invention is naturally applicable for use in aliquid crystal display device that adopts any other driving method.

(Edge Portion and Central Portion)

First, misalignment that may occur in an electrode edge portion will bedescribed.

The present inventors discovered that when a voltage was applied to aliquid crystal display device including a vertical alignment liquidcrystal layer, of which the pretilt direction was controlled using analignment film, to present a gray scale level thereon, an area, whichlooked darker than the gray scale level being presented when viewedstraight, appeared inside of, and substantially parallel to, an edgeportion of a pixel electrode. In the multi-domain structure, if at anyof the edges of a pixel electrode, to which a liquid crystal domain islocated close, the azimuthal direction that is perpendicular to the edgeand that points toward the inside of the pixel electrode defines anangle greater than 90 degrees with respect to the tilt direction (i.e.,the reference alignment direction) of the liquid crystal domain, thearea that looks darker than the gray scale level being presented willappear inside of, and substantially parallel to, that edge. Thealignment state of the liquid crystal molecules will be disturbed inthat area probably because the tilt direction of the liquid crystaldomain and the direction in which the anchoring force is produced by anoblique electric field at the edge of the pixel electrode have opposingcomponents.

As used herein, the “gray scale level” refers to any level except black(i.e., the lowest level) and white (i.e., the highest level). The darkarea always appears when a non-black gray scale level (including white)is presented as a matter of principle. However, the dark area is easierto perceive at a relatively high gray scale level. Also, unless aparticular viewing direction is specified, the display state is alwayssupposed to be a front viewing state (i.e., when the screen is viewedperpendicularly by a viewer located right in front of the screen).

The quadruple pixel region 10 shown in FIG. 1 will be described. FIG. 1illustrates a pixel region 10 provided for a substantially square pixelelectrode for the sake of simplicity. However, the present invention isin no way limited to any particular shape of a pixel region.

The pixel region 10 includes four liquid crystal domains A, B, C and D,of which the tilt directions (i.e. reference alignment directions) areidentified by t1, t2, t3 and t4, respectively. These four tiltdirections are defined such that an angle formed between any two of thefour directions is approximately equal to an integral multiple of 90degrees. This is an ideal quadruple structure to achieve the bestviewing angle characteristic because the areas of these liquid crystaldomains A, B, C and D are equal to each other. The four liquid crystaldomains A, B, C and D are arranged in two columns and two rows to definea matrix pattern.

The pixel electrode has four edges (or sides) SD1, SD2, SD3 and SD4. Anoblique electric field to be generated responsive to a voltage appliedproduces an anchoring force that has a component that is perpendicularto any of these sides and that points toward the inside of the pixelelectrode (in an azimuthal direction). In the example shown in FIG. 1,the azimuthal directions that are perpendicular to the four edges SD1,SD2, SD3 and SD4 and that point toward the inside of the pixel electrodeare identified by e1, e2, e3 and e4, respectively.

Each of the four liquid crystal domains is close to two out of the fouredges of the pixel electrode. While a voltage is being applied thereto,each liquid crystal domain is subjected to the anchoring forces thathave been produced at those edges by the oblique electric field.

In an edge portion EG1 of one edge of the pixel electrode, to which theliquid crystal domain A is located close, the azimuthal direction e1that is perpendicular to the edge portion EG1 and that points toward theinside of the pixel electrode defines an angle greater than 90 degreeswith respect to the tilt direction t1 of the liquid crystal domain, andmisalignment occurs in that area. As a result, when a voltage is appliedthereto, the liquid crystal domain A produces an area that looks darkerthan the other areas (which will be referred to herein as a “domain lineDL1”) parallel to this edge portion EG1. It should be noted that in thiscase, the two polarizers are arranged so as to face each other with theliquid crystal layer interposed between them and to have theirtransmission axes (polarization axes) crossed at right angles. That isto say, one of the two polarization axes is arranged horizontally andthe other vertically. The transmission axes of the polarizers aresupposed to be arranged in this manner unless otherwise stated.

In the same way, in an edge portion EG2 of one edge of the pixelelectrode, to which the liquid crystal domain B is located close, theazimuthal direction e2 that is perpendicular to the edge portion EG2 andthat points toward the inside of the pixel electrode defines an anglegreater than 90 degrees with respect to the tilt direction t2 of theliquid crystal domain, and misalignment occurs in that area. As aresult, when a voltage is applied thereto, the liquid crystal domain Bmay produce an area that looks darker than the other areas (which willbe referred to herein as a “domain line DL2”) parallel to this edgeportion EG2.

In the same way, in an edge portion EG3 of one edge of the pixelelectrode, to which the liquid crystal domain C is located close, theazimuthal direction e3 that is perpendicular to the edge portion EG3 andthat points toward the inside of the pixel electrode defines an anglegreater than 90 degrees with respect to the tilt direction t3 of theliquid crystal domain, and misalignment occurs in that area. As aresult, when a voltage is applied thereto, the liquid crystal domain Cmay produce an area that looks darker than the other areas (which willbe referred to herein as a “domain line DL3”) parallel to this edgeportion EG3.

In the same way, in an edge portion EG4 of one edge of the pixelelectrode, to which the liquid crystal domain D is located close, theazimuthal direction e4 that is perpendicular to the edge portion EG4 andthat points toward the inside of the pixel electrode defines an anglegreater than 90 degrees with respect to the tilt direction t4 of theliquid crystal domain, and misalignment occurs in that area. As aresult, when a voltage is applied thereto, the liquid crystal domain Dmay produce an area that looks darker than the other areas (which willbe referred to herein as a “domain line DL4”) parallel to this edgeportion EG4.

If the horizontal direction on a display screen (i.e., the three o'clockdirection) has an azimuthal angle of zero degrees, the tilt directionst1, t2, t3 and t4 are an approximately 225 degree direction (liquidcrystal domain A), an approximately 315 degree direction (liquid crystaldomain B), an approximately 45 degree direction (liquid crystal domainC) and an approximately 135 degree direction (liquid crystal domain D),respectively. The liquid crystal domains A, B, C and D are arranged suchthat the tilt directions of any two adjacent ones of the liquid crystaldomains define an angle of approximately 90 degrees between them. Theangle defined by any of the tilt directions t1, t2, t3 and t4 of theliquid crystal domains A, B, C and D with respect to an associated oneof the azimuth angle components e1, e2, e3 and e4 of the anchoringforces produced by the oblique electric fields at the nearby edgeportions EG1, EG2, EG3 and EG4 is approximately 135 degrees.

The dark areas (i.e., the domain lines DL1 through DL4) that areproduced parallel to the edge portions EG1, EG2, EG3 and EG4,respectively, within the pixel region 10 deteriorate the viewing anglecharacteristic as will be described later. Thus, by providing opaqueportions that can selectively shield at least respective parts of theseedge portions EG1 through EG4 from incoming light, the deterioration ofthe viewing angle characteristic can be minimized.

As used herein, “to shield an edge portion from incoming light” meansshielding not only the edge portion EG1, EG2, EG3 or EG4 but also itsassociated dark area (i.e., the domain line DL1, DL2, DL3 or DL4)produced near the edge portion in the pixel region from incoming light.The location of each domain line (i.e., the distance from its associatededge portion of the pixel electrode) is changeable with the dimensionsof the pixel electrode, for example. Typically, however, the opaqueportion may be arranged so as to shield a range that reachesapproximately 10 μm to 20 μm from any edge portion of the pixelelectrode from incoming light. Also, “an opaque portion for selectivelyshielding an area from incoming light” means that the opaque portion isprovided to shield only that area selectively from incoming light.Nevertheless, there is no need to isolate such an opaque portion forselectively shielding an area from incoming light from the other opaqueportions. To minimize the deterioration in viewing angle characteristic,the opaque portions are preferably arranged so as to shield all of thedomain lines from incoming light. However, the presence of the opaqueportions would decrease the optical efficiency (represented by theeffective aperture ratio of a pixel). If an opaque portion that shieldsat least a part of an edge portion (including a domain line producedaround there) from incoming light is provided, then the deterioration inviewing angle characteristic can be lightened at least to that degree.That is why the portions to shield from incoming light may be determinedso as to strike an adequate balance between the required performance ofthe LCD and the optical efficiency to achieve.

Typically, an opaque portion is arranged so as to shield an edge portionand a domain line, which is produced near the edge portion in the pixelregion, from incoming light. However, if the pixel aperture ratio shouldbe given a higher priority than the viewing angle characteristic tostrike a proper balance between them, only a part or all of the domainline may be shielded from incoming light without shielding the edgeportion in order to reduce the area of the opaque portion. In most ofthe embodiments to be described below, the edge portion and all of thedomain line are supposed to be shielded from incoming light. However, inany of those embodiments, the viewing angle characteristic can beimproved by providing an opaque portion that selectively shields atleast a portion of the domain line.

A method of dividing a pixel region into these four liquid crystaldomains A through D (i.e., the arrangement of the liquid crystal domainsin the pixel region) is not limited to the example illustrated inFIG. 1. Alternative alignment division methods (or alternativearrangements of liquid crystal domains) will be described with referenceto FIGS. 2 through 5.

FIG. 2( a) shows a method of dividing the pixel region 10 shown inFIG. 1. More specifically, the pretilt directions PA1 and PA2 defined bythe alignment film of a TFT substrate (i.e., the lower substrate), thepretilt directions PB1 and PB2 defined by the alignment film of a colorfilter (CF) substrate (i.e., the upper substrate), the tilt directionsdefined responsive to the application of a voltage to the liquid crystallayer, and areas that look dark due to misalignment (i.e., domain linesDL1 through DL4) are shown in FIG. 2( a). Those areas are not so-called“disclination lines”. These drawings schematically indicate theorientation directions of liquid crystal molecules as viewed by theviewer and show that the liquid crystal molecules are tilted such thatthe elliptical end of each cylindrical liquid crystal molecule pointstoward the viewer.

By conducting an alignment treatment so as to achieve the alignmentstate shown in FIG. 2( a), the pixel region 10 can be defined.Specifically, the alignment treatment is conducted so as to divide thepixel region close to the TFT substrate into two and to define thepretilt directions PAL and PA2 that are antiparallel to the verticalalignment film. In this embodiment, a photo-alignment treatment iscarried out by irradiating the liquid crystal layer with an ultravioletray obliquely that has come from the direction pointed by the arrows.The alignment treatment is also conducted so as to divide the pixelregion close to the CF substrate into two and to define the pretiltdirections PB1 and PB2 that are antiparallel to the vertical alignmentfilm. By attaching these substrates together, a multi-domain structurecan be defined in the pixel region 10. In the photo-alignment treatment,the light does not have to come from the directions indicated above.Alternatively, the pixel region on the CF substrate may be irradiatedwith a light ray that has come from a direction that is tilted withrespect to the vertical direction (i.e., the column direction) and thepixel region on the TFT substrate may be irradiated with a light raythat has come from a direction that is tilted with respect to thehorizontal direction (i.e., the row direction).

As already described with reference to FIG. 1, the domain lines DL1,DL2, DL3 and DL4 are produced in the liquid crystal domains A, B, C andD parallel to the edge portions EG1, EG2, EG3 and EG4, respectively. Thesum of the lengths of these four domain lines DL1 through DL4 will be anapproximately half of the overall length of the four edges of the pixelelectrode. The edge portions EG1 and EG3 (with the domain lines DL1 andDL3) are parallel to the vertical direction, while the edge portions EG2and EG4 (with the domain lines DL2 and DL4) are parallel to thehorizontal direction.

As shown in FIG. 2( a), a dark line is also observed in the boundaryarea of each of the liquid crystal domains A through D, which isadjacent to another one of the liquid crystal domains A through D, asindicated by the dashed line CL1. As will be described later, thecrossed dark lines formed around the center of the pixel region are notalways misalignment and do not have to be shielded on purpose. However,if an opaque member needs to be arranged within the pixel region, theopaque member is preferably arranged to hide these dark lines becausethe effective aperture ratio of the pixel (i.e., the optical efficiency)can be increased in that case.

Alternatively, by attaching together the TFT and CF substrates that havebeen subjected to the alignment treatment as shown in FIG. 2( b), amulti-domain structure can be defined for a pixel region 20. This pixelregion 20 also includes four liquid crystal domains A, B, C and D. Thetilt directions of the liquid crystal domains A through D are the sameas those of the liquid crystal domains of the pixel region 10 shown inFIG. 1.

The domain lines DL1, DL2, DL3 and DL4 are produced in the liquidcrystal domains A, B, C and D parallel to the edge portions EG1, EG2,EG3 and EG4, respectively. The sum of the lengths of these four domainlines DL1 through DL4 will be an approximately half of the overalllength of the four edges of the pixel electrode. The edge portions EG1and EG3 (with the domain lines DL1 and DL3) are parallel to thehorizontal direction, while the edge portions EG2 and EG4 (with thedomain lines DL2 and DL4) are parallel to the vertical direction. Asshown in FIG. 2( b), a dark line is also observed in the boundary areaof each of the liquid crystal domains A through D, which is adjacent toanother one of the liquid crystal domains A through D, as indicated bythe dashed line CL1. These dark lines are produced in the shape of across around the center of the pixel region.

Alternatively, by attaching together the TFT and CF substrates that havebeen subjected to the alignment treatment as shown in FIG. 3( a), amulti-domain structure can be defined for a pixel region 30. This pixelregion 30 also includes four liquid crystal domains A, B, C and D. Thetilt directions of the liquid crystal domains A through D are the sameas those of the liquid crystal domains of the pixel region 10 shown inFIG. 1.

The tilt directions t1 and t3 of the liquid crystal domains A and C donot point toward any edge portions of the pixel electrode, andtherefore, no domain lines are produced in these liquid crystal domains.On the other hand, the tilt directions t2 and t4 of the liquid crystaldomains B and D point toward their associated edge portions of the pixelelectrode and define an angle greater than 90 degrees with respect toazimuthal directions that are perpendicular to the edge portions andthat point toward the inside of the pixel electrode. As a result, domainlines DL2 and DL4 are produced. Each of the domain lines DL2 and DL4includes a portion (H) that is parallel to the horizontal direction anda portion (V) that is parallel to the vertical direction. That is tosay, each of the tilt directions t2 and t4 defines an angle greater than90 degrees with respect to both an azimuthal direction that isperpendicular to an edge portion of the horizontal edge and that pointstoward the inside of the pixel electrode and an azimuthal direction thatis perpendicular to an edge portion of the vertical edge and that pointstoward the inside of the pixel electrode. Consequently, domain lines areproduced in both of the two directions. As shown in FIG. 3( a), a darkline is also observed in the boundary area of each of the liquid crystaldomains A through D, which is adjacent to another one of the liquidcrystal domains A through D, as indicated by the dashed line CL1. Thesedark lines are produced in the shape of a cross around the center of thepixel region.

Alternatively, by attaching together the TFT and CF substrates that havebeen subjected to the alignment treatment as shown in FIG. 3( b), amulti-domain structure can be defined for a pixel region 40. This pixelregion 40 also includes four liquid crystal domains A, B, C and D. Thetilt directions of the liquid crystal domains A through D are the sameas those of the liquid crystal domains of the pixel region 10 shown inFIG. 1.

The tilt directions t1 and t3 of the liquid crystal domains A and Cpoint toward their associated edge portions of the pixel electrode anddefine an angle greater than 90 degrees with respect to azimuthaldirections that are perpendicular to the edge portions and that pointtoward the inside of the pixel electrode. As a result, domain lines DL1and DL3 are produced. Each of the domain lines DL1 and DL3 includes aportion DL1(H) or DL3(H) that is parallel to the horizontal directionand a portion DL1(V) or DL3(V) that is parallel to the verticaldirection. That is to say, each of the tilt directions t1 and t3 definesan angle greater than 90 degrees with respect to both an azimuthaldirection that is perpendicular to an edge portion of the horizontaledge and that points toward the inside of the pixel electrode and anazimuthal direction that is perpendicular to an edge portion of thevertical edge and that points toward the inside of the pixel electrode.Consequently, domain lines are produced in both of the two directions.On the other hand, the tilt directions t2 and t4 of the liquid crystaldomains B and D do not point toward any edge portions of the pixelelectrode, and therefore, no domain lines are produced in these liquidcrystal domains. As shown in FIG. 3( b), a dark line is also observed inthe boundary area of each of the liquid crystal domains A through D,which is adjacent to another one of the liquid crystal domains A throughD, as indicated by the dashed line CL1. These dark lines are produced inthe shape of a cross around the center of the pixel region.

Alternatively, by attaching together the TFT and CF substrates that havebeen subjected to the alignment treatment as shown in FIG. 4( a), amulti-domain structure can be defined for a pixel region 50. This pixelregion 50 also includes four liquid crystal domains A, B, C and D. Thetilt directions of the liquid crystal domains A through D are the sameas those of the liquid crystal domains of the pixel region 10 shown inFIG. 1.

The tilt directions t1, t2, t3 and t4 of all of these liquid crystaldomains A, B, C and D point toward their associated edge portions of thepixel electrode and define an angle greater than 90 degrees with respectto azimuthal directions that are perpendicular to the edge portions andthat point toward the inside of the pixel electrode. As a result, domainlines DL1 DL2, DL3 and DL4 are produced. Each of the domain lines DL1through DL4 includes a portion DL1(H), DL2(H), DL3(H) or DL4(H) that isparallel to the horizontal direction and a portion DL1(V), DL2(v),DL3(V) or DL4(V) that is parallel to the vertical direction. That is tosay, each of the tilt directions t1 through t4 defines an angle greaterthan 90 degrees with respect to both an azimuthal direction that isperpendicular to an edge portion of the horizontal edge and that pointstoward the inside of the pixel electrode and an azimuthal direction thatis perpendicular to an edge portion of the vertical edge and that pointstoward the inside of the pixel electrode. Consequently, domain lines areproduced in both of the two directions. As shown in FIG. 4( a), a darkline is also observed in the boundary area of each of the liquid crystaldomains A through D, which is adjacent to another one of the liquidcrystal domains A through D, as indicated by the dashed line CL1. Thesedark lines are produced in the shape of a cross around the center of thepixel region.

Alternatively, by attaching together the TFT and CF substrates that havebeen subjected to the alignment treatment as shown in FIG. 4( b), amulti-domain structure can be defined for a pixel region 60. This pixelregion 60 also includes four liquid crystal domains A, B, C and D. Thetilt directions of the liquid crystal domains A through D are the sameas those of the liquid crystal domains of the pixel region 10 shown inFIG. 1.

None of the tilt directions t1, t2, t3 and t4 of the liquid crystaldomains A through D point toward any edge portions of the pixelelectrode, and therefore, no domain lines are produced at all in theseliquid crystal domains. A dark line is also observed in the boundaryarea of each of the liquid crystal domains A through D, which isadjacent to another one of the liquid crystal domains A through D, asindicated by the dashed line CL1. These dark lines are produced in theshape of a cross around the center of the pixel region.

In each of the four-domain structures described above, four liquidcrystal domains are arranged in two columns and two rows to define amatrix pattern. However, the present invention is in no way limited tothat specific embodiment. Alternatively, the four liquid crystal domainsmay be arranged in line in a predetermined direction as shown in FIGS.5( a) and 5(b), in which the liquid crystal domains are arranged in linein the column direction.

The pixel region 70 shown in FIG. 5( a) also includes four liquidcrystal domains A, B, C and D. The tilt directions of the liquid crystaldomains A through D are the same as those of the liquid crystal domainsof the pixel region 10 shown in FIG. 1. The tilt directions t1, t2, t3and t4 of all of these liquid crystal domains A, B, C and D point towardtheir associated edge portions of the pixel electrode and define anangle greater than 90 degrees with respect to azimuthal directions thatare perpendicular to the edge portions and that point toward the insideof the pixel electrode. As a result, domain lines DL1, DL2, DL3 and DL4are produced. All of these domain lines DL1 through DL4 are parallel tothe vertical direction (i.e., the direction in which the liquid crystaldomains are arranged). A dark line is also observed in the boundary areaof each of the liquid crystal domains A through D, which is adjacent toanother one of the liquid crystal domains A through D. These dark linesare produced horizontally (i.e., perpendicularly to the direction inwhich the liquid crystal domains are arranged) around the center of thepixel region.

On the other hand, in the pixel region 80 shown in FIG. 5( b), the tiltdirections of the four liquid crystal domains A′, B′, C′ and D′ are 90degrees, 180 degrees, 0 degrees and 270 degrees, respectively, as shownin that drawing. The domain lines DL1′ and DL4′ of the liquid crystaldomains A′ and D′ are parallel to the horizontal direction. And thedomain lines DL2′ and DL3′ are parallel to the vertical direction. Adark line is also observed in the boundary area of each of the liquidcrystal domains A′ through D′, which is adjacent to another one of theliquid crystal domains A′ through D′. These dark lines are producedhorizontally (i.e., perpendicularly to the direction in which the liquidcrystal domains are arranged) around the center of the pixel region. Ifthe tilt directions are defined in this manner, the polarizers arepreferably arranged such that their transmission axes define angles of±45 degrees with respect to the horizontal direction.

Next, it will be described with reference to FIGS. 6 through 9 howdomain lines are produced near the edge portions of a pixel electrodeand how dark lines are produced (in the shape of a cross as shown inFIG. 2, for example) around the center of the pixel region. FIGS. 6through 9 are cross sectional views of a pixel region of a liquidcrystal display device, showing the equipotential curve of an electricfield created in the liquid crystal layer 3, the orientation directionsof liquid crystal molecules 3 a in the layer, and the relative (front)transmittance thereof, which were figured out by simulations.

This liquid crystal display device includes a TFT substrate 1 includinga transparent substrate (e.g., a glass substrate) 1 a and a pixelelectrode 11 on the transparent substrate 1 a, a CF substrate 2including a transparent substrate (e.g., a glass substrate) 2 a and acounter electrode 12 on the transparent substrate 2 a, and a verticalalignment liquid crystal layer 3 interposed between the TFT and CFsubstrates 1 and 2. A vertical alignment film (not shown) is provided oneach of the TFT and CF substrates 1 and 2 so as to contact with theliquid crystal layer 3. The liquid crystal layer is subjected to analignment treatment so as to have the pretilt directions controlled asindicated by the arrows, arrowheads and arrow tails in FIGS. 6 to 9.

First, referring to FIG. 6, illustrated is a cross sectional view of theleft half of the pixel region 20 shown in FIG. 2( b), including an edgeportion of the liquid crystal domain D with the domain line DL4, asviewed on a plane defined by an azimuth angle of zero degrees. It can beseen that at an edge portion of the pixel electrode 11 shown in FIG. 6,liquid crystal molecules 3 a (with a tilt angle of 135 degrees), locatedaround the center of a plane of the liquid crystal domain andapproximately at the middle of the thickness thereof, are graduallytwisted toward the edge portion of the pixel electrode under theanchoring force (defined by an azimuthal direction of zero degrees) ofan oblique electric field generated in the edge portion of the pixelelectrode 11. In this example, the twist angle is 135 degrees, which isgreater than 90 degrees. That is why due to a variation in retardationin this twisting region of the liquid crystal layer, the relativetransmittance varies in a complicated manner as shown in FIG. 6, therebyproducing a domain line in which the relative transmittance becomeslocal minimum within the pixel region (i.e., inside of the edge of thepixel electrode). That region with the local minimum transmittance asindicated by the dotted square in FIG. 6 corresponds to the domain lineDL4 in the liquid crystal domain D shown in FIG. 2( b).

On the other hand, in another edge portion of the pixel electrode inwhich no domain line is produced as shown in FIG. 7, the twist angle ofthe liquid crystal molecules (i.e., the difference in tilt directionbetween the liquid crystal molecules located around the center of theliquid crystal domain and the liquid crystal molecules, of which thealignment is controlled by an oblique electric field that has beengenerated in the edge portion of the pixel electrode 11) is 90 degreesor less. And the relative transmittance decreases monotonically from thecentral portion of the pixel region toward the end thereof and reachesits local minimum outside of the pixel region (i.e., at the left end ofFIG. 7), not inside of the pixel region. FIG. 7 is a cross-sectionalview of the lower half of the pixel region 20 shown in FIG. 2( b),including another edge portion of the liquid crystal domain D withoutthe domain line DL4, as viewed on a plane defined by an azimuth angle of90 degrees.

Meanwhile, as shown in FIGS. 8 and 9, the liquid crystal molecules alsohave a twist angle of 90 degrees or less in the boundary area in whichtwo liquid crystal domains are adjacent to each other within the pixelregion. Thus, the relative transmittance also changes simply and reachesa local minimum value there. FIG. 8 is a cross-sectional view of theliquid crystal domains D and A shown in FIG. 2( b), including theboundary area between them, as viewed on a plane defined by an azimuthangle of zero degrees. FIG. 9 is a cross-sectional view of the liquidcrystal domains B and A shown in FIG. 4( b), including the boundary areabetween them, as viewed on a plane defined by an azimuth angle of zerodegrees.

FIG. 10 shows the distributions of transmission intensities in asituation where the pixel region 10 is viewed from the direction definedby an azimuth angle of 45 degrees. The four graphs of FIG. 10 show thedistributions of transmission intensities on the four planes I, II, IIIand IV, respectively. Also, each of these graphs shows results in threeviewing directions defined by polar angles of zero degrees (i.e., frontdirection), 45 degrees and 60 degrees, respectively.

It can be seen that in the domain lines appearing at the left end ofGraph I, at the right end of Graph II, at the right end of Graph III,and at the left end of Graph IV, the behavior of the transmissionintensity changes significantly according to the polar angle(particularly in Graph III). That is to say, the location with theminimum transmission intensity changes with the polar angle. Forexample, the transmission intensity in the front viewing direction(defined by a polar angle of zero degrees) is local minimum, whereas thetransmission intensities at the polar angles of 45 and 60 degrees arelocal maximum. If the transmission intensity changes according to thepolar angle in this manner, the viewing angle characteristicdeteriorates. Among other things, the viewing angle dependence of γcharacteristic deteriorates significantly to cause a phenomenon called“whitening”.

By providing opaque portions that can selectively shield at leastrespective portions of the domain lines, produced in the edge portionsof the pixel electrode, from incoming light, such deterioration inviewing angle characteristic can be reduced. Also, those domain linesare produced in the edge portions when the tilt directions of the liquidcrystal molecules around the center of the liquid crystal layer aredefined as described above with respect to the edges of the electrode.That is why the domain lines may also be produced in a normal pixelregion with no multi-domain structures. For that reason, to minimize thedeterioration in viewing angle characteristic due to the production ofdomain lines in the edge portions of the pixel electrode, such opaqueportions for selectively shielding at least respective portions of thedomain lines are preferably provided, no matter whether the multi-domainstructure should be formed or not.

The dark lines formed around the center of the pixel region (e.g.,crossed lines CL1) are not always misalignment and do not have to beshielded on purpose. However, if an opaque member needs to be arrangedwithin the pixel region, the opaque member is preferably arranged tohide these dark lines because the effective aperture ratio of the pixel(i.e., the optical efficiency) can be increased in that case.

Hereinafter, embodiments of opaque portions will be describedspecifically. Each of the opaque portions to be described below may beused either by itself or in combination with any other opaque portion.

A TFT LCD usually includes an opaque member. For example, a TFTsubstrate includes a gate bus line, a source bus line, a drain extensionline and a storage capacitor line (which will be referred to herein as a“CS bus line”). Also, a CF substrate includes a black matrix to shieldthe surrounding areas of color filters that are arranged so as tooverlap with pixel regions. The opaque portions for selectivelyshielding at least portions of the domain lines may be defined by usingthese opaque members. Furthermore, to minimize the decrease in opticalefficiency caused by the opaque member arranged within the pixel region,the opaque member is preferably arranged so as to hide the dark areaproduced between adjacent liquid crystal domains.

Hereinafter, an exemplary pixel structure for a liquid crystal displaydevice according to the present invention will be described. In thedrawings, any pair of components shown in multiple drawings and havingsubstantially the same function is identified by the same referencenumeral. And once a component has been described, the description of itscounterpart will be omitted herein to avoid redundancies. Also, in anumber of pixels that are arranged in columns and rows so as to form amatrix pattern, the structure of a pixel located at an intersectionbetween an m^(th) row and an n^(th) column will be described. It shouldbe noted that a row corresponds to an arrangement of pixels along a gatebus line (or scan line), while a column corresponds to an arrangement ofpixels along a source bus line (or signal line). Typically, rows aredefined in the horizontal direction on the display screen, while columnsin the vertical direction on the display screen.

The opaque portions may be defined by using at least portions of thesource bus line 114, the CS bus line 113, the drain extension line 117and the gate bus line 112 as shown in FIG. 11, for example. In thefollowing description, an m^(th) gate bus line 112 will be referred toherein as a “gate bus line 112(m)” and an n^(th) source bus line 114will be referred to herein as a “gate bus line 114(n)”.

The pixel region shown in FIG. 11 illustrates a subpixel with themultipixel structure disclosed in Japanese Patent Application Laid-OpenPublication No. 2004-62146. The following description will be focused onthe structure of the upper one of the two subpixel regions that has thesubpixel electrode 111 a.

The sub-pixel electrode 111 a is connected to the drain electrode 116Dof the TFT 116 and is arranged so as to partially overlap with thesource bus line 114, the gate bus line 112 and the CS bus line 113 withan interlayer dielectric film (not shown) of resin interposed betweenthem. Also, at the center of the sub-pixel electrode 111 a, a storagecapacitor CS is formed by an extended portion 117E of the drainextension line 117, an extended portion 113E of the CS bus line 113 andan insulating layer (e.g., a gate insulating layer) between them.

The multipixel structure shown in FIG. 11 has the following features.

The conventional pixel electrode is divided into two subpixelelectrodes, which are connected to the same source bus line 114 by wayof their associated TFTs 116 a and 116 b (i.e., two TFTs in total). TheON and OFF states of the two TFTs 116 a and 116 b are controlled throughthe common gate bus line 112. The two TFTs 116 a and 116 b share asemiconductor layer 116 m, a source electrode 116S, and a gate electrode(gate bus line 112) in common. And the respective drain electrodes 116Dof the two TFTs are electrically connected to their associated subpixelelectrodes. The drain electrode 116D of the TFT 116 a and the subpixelelectrode 111 a are electrically connected together by connecting thedrain extension line 117, extending from the drain electrode 116D, tothe subpixel electrode 111 a in a contact hole 119 that has been cutthrough an interlayer dielectric film (which is not shown in FIG. 11 butis identified by the reference numeral 118 a in FIG. 15).

Each subpixel electrode (which is the upper subpixel electrode 111 a inFIG. 11 with the lower subpixel electrode not shown there), the liquidcrystal layer, and a counter electrode (common electrode) that facesthese electrodes with the liquid crystal layer interposed between themform a liquid crystal capacitor. Storage capacitors CS are formedelectrically in parallel with the liquid crystal capacitors associatedwith the respective subpixel regions. As for the upper subpixel, one ofthe two electrodes that form the storage capacitor (i.e., the storagecapacitor electrode) is defined by the extended portion 117E of thedrain extension line 117 that is connected to the drain 116D of the sameTFT 116 a as the subpixel electrode 111 a, while the other electrode(i.e., the storage capacitor counter electrode) is defined by theextended portion 113E of the CS bus line 113 provided for the uppersubpixel. Likewise, as for the lower subpixel, one of the two electrodesthat form the storage capacitor (i.e., the storage capacitor electrode)is defined by the extended portion (not shown) of the drain extensionline (not shown) that is connected to the drain (not shown) of the sameTFT 116 b as the lower subpixel electrode (not shown), while the otherelectrode (i.e., the storage capacitor counter electrode) is defined bythe extended portion (not shown) of the CS bus line (not shown) providedfor the lower subpixel.

The CS bus lines 113 are provided electrically independently of eachother for the two subpixels. For example, if the storage capacitorcounter voltage supplied to the storage capacitor belonging to onesubpixel through the CS bus line 113 rises after the TFT 116 a has beenturned OFF, the storage capacitor counter voltage supplied to thestorage capacitor belonging to the other subpixel through the CS busline 113 falls after the TFT 116 b has been turned OFF. If (themagnitudes and/or the directions of) the storage capacitor countervoltages of the storage capacitors belonging to the respective subpixelsare changed differently after their associated TFTs have been turnedOFF, different effective voltages will be applied to the respectiveliquid crystal layers of the two subpixels. As a result, the twosubpixels can present two different luminances (one of which isrelatively high and the other of which is relatively low) with respectto the display signal voltage supplied through the source bus line 114.Consequently, the viewing angle dependence of the γ characteristic canbe reduced.

The sub-pixel region shown in FIG. 11 has a multi-domain structuresimilar to that of the pixel region 10 described above. That is to say,domain lines are produced near the edge portions EG1, EG2, EG3 and EG4of the sub-pixel electrode and crossed dark lines are produced at thecenter of the sub-pixel region.

The opaque portions for selectively shielding at least portions of thedomain lines produced near the edge portions EG1 and EG3 may be formedby bending the source bus line 114 in a direction that crosses itslength direction (the vertical direction), i.e., toward the sub-pixelelectrode. Optionally, the opaque portions may also be formed by locallyincreasing the width of the source bus line 114. However, the opaqueportions are preferably formed by bending the source bus line becausethe stray capacitance might increase if the source bus line had anincreased width.

The domain line produced in the edge portion EG2 may be shielded byincreasing the width of overlap between the edge portion of thesub-pixel electrode 111 a and the gate bus line 112. The overlap widthmay be increased either by partially increasing the width of thesub-pixel electrode 111 a or the gate bus line 112 (e.g., by providingthe broadened portion 111E of the subpixel electrode 111 a shown in FIG.11) or by bending the gate bus line 112 in a direction that crosses itslength direction (i.e., the horizontal direction).

The domain line produced in the edge portion EG4 may be shielded byincreasing the width of overlap between the edge portion of thesub-pixel electrode 111 a and the CS bus line 113. The overlap width maybe increased either by partially increasing the width of the sub-pixelelectrode 111 a or the CS bus line 113 (e.g., by providing the broadenedportion 113A of the CS bus line 113 shown in FIG. 11) or by bending theCS bus line 113 in a direction that crosses its length direction (i.e.,the horizontal direction).

The opaque portions for selectively shielding at least portions of thedark areas produced in the boundary areas between the liquid crystaldomains may be formed by respective extended portions 113 e and 113E ofthe CS bus line 13 and the drain extension line 117 and its extendedportion 117E. By using the storage capacitor CS in the pixel as anopaque portion in this manner, the extra decrease in optical efficiencycan be minimized.

Alternatively, the CS bus line 13 may have not only the extendedportions 113 e and 113E for shielding the crossed dark lines at thecenter of the pixel region but also additional extended portions 113E1and 113E2 for shielding the domain lines produced in the edge portionsEG1 and EG2, respectively, as shown in FIG. 12.

If a multi-domain structure similar to that of the pixel region 30 shownin FIG. 3( a) is formed for the sub-pixel region, then the arrangementshown in FIG. 13 may be adopted, for example.

Specifically, the domain line (DL4(H) shown in FIG. 3( a)) produced inthe horizontal part of the edge portion EG4 may be shielded byincreasing the width of overlap between the CS bus line 13 and thesub-pixel electrode 111 a. The width of overlap can be increased bypartially increasing the width of the sub-pixel electrode 111 a suchthat an extended portion 111E1 is formed. On the other hand, the domainline (DL2(H) shown in FIG. 3( a)) produced in the horizontal part of theedge portion EG2 may be shielded by increasing the width of overlapbetween the gate bus line 112 and the sub-pixel electrode 111 a. Thewidth of overlap can be increased by partially increasing the width ofthe sub-pixel electrode 111 a such that an extended portion 111E2 isformed. The vertical parts of the edge portions EG2 and EG4 (DL2(V) andDL4(V) shown in FIG. 3( a)) may be shielded by the bent portions of thesource bus line 114 as in the example described above.

If a multi-domain structure similar to that of the pixel region 10 isadopted, the opaque portions for shielding the dark areas produced inthe boundary areas between the liquid crystal domains may be defined bythe extended portions 117E and 117E′ of the drain extension line 117 asshown in FIG. 14. The extended portion 117E faces the CS bus line 113 toform a storage capacitor.

FIG. 15 is a cross-sectional view of the structure shown in FIG. 14 asviewed on the plane 15A-15A′ shown in FIG. 14. As shown in FIG. 15, thedrain extension line 117 and the gate bus line 112 interpose a gateinsulating film 115 between them. Thus, leakage is less likely to beproduced between the drain extension line 117 and the gate bus line 112because these belong to two separate layers. A normal pixel with nomultipixel structure is illustrated in FIG. 14. When this arrangement isapplied to a multipixel structure, even if a CS bus line is arranged inplace of the gate bus line 112 in the upper part of FIG. 14, the opaqueportion may also be formed to hide the central cross lines by theextended portions 117E and 117E′ of the drain extension line 117 asshown in FIG. 14, too. The CS bus line 113 is made of the sameconductive layer (which is typically a metal layer) as the gate bus line112. That is why leakage is less likely to be produced between the drainextension line 117 and the CS bus line 113. That is to say, the verticalpart of the opaque portion to form the cross and the horizontal part ofthe opaque portion to shield the horizontal edge portion are preferablymade of two different layers. By adopting such an arrangement, theleakage failures can be reduced compared to the configuration disclosedin FIG. 60 of Patent Document No. 1.

In the pixel structure shown in FIG. 15, a relatively thick interlayerdielectric film 118 a of a photosensitive resin, for example, isinterposed between the pixel electrode 111 and the source bus line 114.That is why even if the pixel electrode 111 (or the subpixel electrode111 a) and the source bus line 114 (and the gate bus line 112) arestacked one upon the other as shown in FIG. 14, the capacitance producedbetween the pixel electrode 111 and the source bus line 114 can bereduced sufficiently. Consequently, the voltage at the pixel electrode111 never varies due to the voltage (i.e., signal voltage) on the sourcebus line 114 by way of the capacitance. That is to say, by adopting thepixel structure shown in FIG. 15 in which the pixel electrode 111 andthe source bus line 114 are stacked one upon the other, the apertureratio of the pixel can be increased.

Alternatively, the domain lines produced in the edge portions and thecrossed dark lines produced around the center of the pixel region may beshielded by the extended portion 113 e of the CS bus line 113 as shownin FIGS. 16 and 17. In the arrangement illustrated in FIGS. 16 and 17, arelatively thin interlayer dielectric film 118 b of an inorganicmaterial such as SiN_(x), for example, is provided between the pixelelectrode 111 and the source bus line 114. In this arrangement, toprevent the voltage at the pixel electrode 111 from being affected bythe voltage (i.e., signal voltage) on the source bus line 114, the pixelelectrode 111 and the bus lines are arranged so as not to overlap eachother. This arrangement does not contribute to increasing the apertureratio of a pixel but can simply the manufacturing process because arelatively thin inorganic insulating film can be used as the interlayerdielectric film 118 b.

As another alternative, the domain lines produced in the edge portionsand the crossed dark lines produced around the center of the pixelregion may also be shielded by extending the drain extension line 117 asshown in FIG. 18. Since the drain extension line 117 belongs to adifferent layer from that of the gate bus line 112 and the CS bus line113 as described above, leakage failures are less likely to occurbetween them. A sub-pixel region with a multipixel structure isillustrated in FIG. 18. However, this structure is equally applicablefor use in a normal pixel region, too.

In each of the examples described above, the opaque portions are definedby using the opaque members arranged on the TFT substrate. If necessary,however, part or all of the opaque portions may be located on the CFsubstrate. For example, opaque portions with relatively broad widths(e.g., the opaque portions for shielding the domain lines produced inthe edge portions parallel to the vertical direction and the opaqueportion for shielding the crossed dark lines produced around the centerof the pixel region) may be defined by the black matrix layer 132 on theCF substrate as shown in FIG. 19. In this example, the horizontallyextending portion of the crossed dark lines around the center of thepixel is supposed to be shielded entirely by the extended portion 132Eof the black matrix layer 132. Alternatively, part of that portion maybe shielded by the black matrix layer 132 and the other part may beshielded by the drain extension line 117. Still alternatively, any ofthe shielding structures and this arrangement may be combinedappropriately.

Optionally, as shown in FIGS. 20 and 21, the crossed dark lines aroundthe center may be shielded by the drain extension line 117 and thedomain lines in the edge portions may be shielded by the extendedportion 113E1 of the CS bus line 113 and the extended portion 112E ofthe gate bus line 112. As for the pixel region shown in FIGS. 20 and 21,only one subpixel of the multipixel structure disclosed in JapanesePatent Application Laid-Open Publication No. 2004-62146 is shown.However, this arrangement can be equally applied to a normal pixelregion, too. Also, in the subpixel region shown in FIGS. 20 and 21, thefour liquid crystal domains shown in FIG. 3( a) are produced.

In the subpixel region shown in FIGS. 20 and 21, there is a drainextension line 117 that is connected to the drain 116D of the TFT 116 a,thereby shielding the crossed dark lines around the center of thesubpixel region. A gate bus line extended portion 112E is also providedso as to branch from the gate bus line 112 and to include a part thatfaces the drain extension line 117 connected to the TFT 116 with aninsulating layer (which is typically a gate insulating film) interposedbetween them. That part of the extended portion 112E of the gate busline 112 that faces the drain extension line 117 produces a capacitor124 a. This capacitor 124 a is a component of the gate-drain capacitanceCgd of the TFT in the subpixel region, and will be referred to herein asa “Cgd compensating capacitor 124 a”.

In the example shown in FIG. 20, the lower end portion of the drainextension line 117 overlaps with the extended portion 112E of the gatebus line 112. That is why if the drain extension line 117 has misalignedvertically, the Cgd compensating capacitor 124 a will have itscapacitance value varied. In a portion of the TFT 116 where a Cgdparasitic capacitor 122 a is formed, the lower end portion of the drainextension line 117 (i.e., the drain electrode 116D) overlaps with thegate electrode (i.e., a portion of the gate bus line 112 in thisexample). That is why if the drain extension line 117 (drain electrode116D) has misaligned vertically, the Cgd parasitic capacitor 122 a willhave its capacitance value varied.

On the other hand, in the example shown in FIG. 21, the right endportion of the drain extension line 117 overlaps with the extendedportion 112E of the gate bus line 112. That is why if the drainextension line 117 has misaligned horizontally, the Cgd compensatingcapacitor 124 a will have its capacitance value varied. In a portion ofthe TFT 116 where a Cgd parasitic capacitor 122 a is formed, the leftend portion of the drain extension line 117 (i.e., the drain electrode116D) overlaps with the gate electrode 116G (i.e., a portion branchingfrom the gate bus line 116 in this example). That is why if the drainextension line 117 (drain electrode 116D) has misaligned horizontally,the Cgd parasitic capacitor 122 a will have its capacitance valuevaried. The right end portion of the drain extension line 117 that formsthe Cgd compensating capacitor 124 a and the left end portion of thedrain extension line 117 that forms the Cgd parasitic capacitor 122 aare located on opposite sides horizontally. That is why if the drainextension line 117 (drain electrode 116D) has misaligned horizontally,one of the Cgd compensating capacitor 122 a and the Cgd parasiticcapacitor 124 a increases its capacitance value but the other capacitordecreases its capacitance value. For that reason, if the drain extensionline 117 has substantially equal widths at the right and left endsthereof, the sum of the Cgd capacitances (=the Cgd parasitic capacitanceof the TFT portion+the Cgd compensating capacitance) can be keptconstant even when the drain extension line 117 misaligns horizontally.

In the subpixel region shown in FIGS. 20 and 21, the four liquid crystaldomains shown in FIG. 3( a) are produced. That is why as in thearrangement shown in FIG. 13, opaque portions for selectively shieldingthe domain lines DL2 (including DL2(H) and DL2(V)) and the domain linesDL4 (including DL4(H) and DL4(V)) are preferably formed. In addition, acentral opaque portion for selectively shielding the boundary regions(i.e., CL1 in FIG. 3( a)) where each of the four liquid crystal domainsis adjacent to another one is also preferably provided.

In this example, the extended portion 112E of the gate bus line 112provided in the subpixel region forms at least a part of the opaqueportion for shielding DL2(V) shown in FIG. 3( a). Also, at least a partof the opaque portion for shielding DL4(V) in the subpixel region shownin FIG. 3( a) is defined by the extended portion 113E1 of the CS busline 113. On the other hand, the domain line DL4(H) shown in FIG. 3( a)is shielded by increasing the width of the overlapping portion betweenthe CS bus line 113 and the subpixel electrode 111 a with the extendedportion 111E1 defined by partially increasing the width of the subpixelelectrode 111 a (upward in this example). In addition, the extendedportion 117E of the drain extension line 117 is provided in a regionincluding the extended portion 111E1 of the subpixel electrode 111 a,thereby forming a storage capacitor CS and contributing to shielding theedge portion EG4. Meanwhile, DL2(H) shown in FIG. 3( a) is shielded byincreasing the width of the overlapping portion between the gate busline 112 and the subpixel electrode 111 a with the extended portion111E2 formed by partially increasing the width of the subpixel electrode111 a (e.g., downward in this example).

Also, in the LCD manufacturing process of the embodiment describedabove, at least the substrate with the opaque portions is preferablyirradiated with light (typically an ultraviolet ray) for the purpose ofphoto-alignment treatment. The opaque portions described above areprovided in areas where misalignment may arise in the multi-domainstructure. That is why if the opaque portions were provided for theother substrate to face the substrate that has been irradiated withlight to define the multi-domain structure, then an alignment errorshould be considered when those substrates are attached together and thesize of the opaque portions should be increased excessively, which isnot beneficial. Also, the substrate is preferably irradiated with lightthat has come from a direction in which the light is not affected by theunevenness on the surface of the substrate. For example, if the CFsubstrate is irradiated with light, the light preferably comes from thecolumn direction. Then, no shadow areas would be produced by the blackmatrix that is arranged between the rows.

(Intersection)

The present inventors discovered that at the intersections OD betweenthe domain lines produced in the edge portions and the boundary areasbetween adjacent liquid crystal domains, the liquid crystal moleculeshad particularly inconsistent orientations and noticeably low responsespeeds as shown in FIG. 22. For that reason, in an application that paysmuch attention to moving picture display performance, those areassurrounding the intersections OD where the liquid crystal molecules haveinconsistent orientations are preferably shielded.

Those intersections OD are preferably shielded by providing extensionsTR1, TR2, TR3 and TR4 that protrude out of the opaque portions forshielding the domain lines produced in the edge portions and the opaqueportions for shielding the boundary area between adjacent liquid crystaldomains as shown in FIG. 23. Specifically, the extensions TR1 and TR3are extended from the CS bus line extended portion 113E, the extensionTR2 is extended from the gate bus line 112, and the extension TR4 isextended from the CS bus line 113. If necessary, it is naturallypossible to shield only the intersections OD selectively. The extensionsTR1 through TR4 shown in FIG. 22 have an almost triangular shape.However, the extensions may have any other shape as long as the opticalefficiency (or aperture ratio) does not decrease unnecessarily. In viewof this consideration, the extensions preferably have such a triangularshape as shown in FIG. 21.

(Partial Shielding)

The liquid crystal display device of the embodiment described aboveincludes opaque portions for shielding edge portions with domain linessubstantially entirely. However, the present invention is in no waylimited to that specific embodiment. To minimize the deterioration inviewing angle characteristic, the opaque portions are preferablyarranged so as to shield the domain lines from incoming light entirelyas described above. If the opaque portions were present, however, theoptical efficiency (i.e., the effective aperture ratio of a pixel) woulddecrease. That is why the edge portions may be shielded partially tostrike an adequate balance between the viewing angle characteristic andthe optical efficiency.

Particularly if an arrangement in which the pixel electrode does notoverlap with the source bus line as viewed perpendicularly to thesubstrate (see the cross-sectional view shown in FIG. 17, for example)is adopted, the pixel aperture ratio decreases. For that reason, toavoid a significant decrease in pixel aperture ratio, the opaque areasare preferably as small as possible. If a relatively thick interlayerdielectric film 118 a of a photosensitive resin, for example, isinterposed between the pixel electrode 111 and the source bus line 114as shown in FIG. 15, the capacitance produced between the pixelelectrode 111 (or the subpixel electrode 111 a) and the source bus line114 (and the gate bus line 112) can be reduced sufficiently even whenthe pixel electrode 111 (or the subpixel electrode 111 a) overlaps withthe source bus line 114 (and the gate bus line 112) as shown in FIGS.14, 18, 19 and 21. That is why the voltage at the pixel electrode 111(or the subpixel electrode 111 a) is not affected by the voltage (i.e.,signal voltage) on the source bus line 114 by way of this capacitance.Consequently, by overlapping the pixel electrode 111 (or the subpixelelectrode 111 a) and the source bus line 114 (and the gate bus line 112)each other, the pixel aperture ratio can be increased.

On the other hand, if an arrangement in which the pixel electrode 111does not overlap with the source bus line 114 (and the gate bus line112) is adopted as shown in the cross-sectional view of FIG. 17, then arelatively thin inorganic insulating film of SiN_(x), for example, maybe used as the interlayer dielectric film 118 b. As a result, themanufacturing process can be simplified, which is advantageous. However,if such an arrangement in which the pixel electrode 111 does not overlapwith the source bus line 114 is adopted, the pixel aperture ratio willdecrease. For that reason, to achieve a sufficient display luminance,the opaque portions are preferably as small as possible.

Hereinafter, exemplary arrangements for shielding only portions of thedomain lines produced in the vicinity of the edge portions of a pixelelectrode and only portions of the crossed dark lines produced aroundthe center of a pixel region will be described with reference to FIGS.24 and 25, which show the upper subpixel region of a pixel with amultipixel structure. The multi-domain structure of the upper subpixelregion is the same as the four-domain structure shown in FIG. 1.

In the example illustrated in FIG. 24, all of the domain lines DL1 andDL4 shown in FIG. 2( a), part of the domain line DL3, and the verticalone of the central dark lines CL1 are shielded, but the domain line DL2and the horizontal one of the central dark lines CL1 are not shielded.In the following description, the vertical one of the central crosseddark lines will be identified herein by CL1 while the horizontal darkline by CL2 as shown in FIG. 26.

The lower half of the opaque portion for selectively shielding CL1 isdefined by the drain extension line 117 and the upper half thereof isdefined by the extended portion 113A3 of the CS bus line 113. The otheropaque portions are defined by the extended portions 113A1, 113A2 and113A4 of the CS bus line 113. Specifically, the extended portion 113A1of the CS bus line 113 is a broadened portion of the CS bus line 113 andthe edge portion EG4 is shielded by increasing the width of theoverlapping portion with the subpixel electrode 111 a. The extendedportion 113A2 of the CS bus line 113 shields the edge portion EG1 andthe extended portion 113A4 of the CS bus line 113 shields approximatelya half of the edge portion EG3. The extended portion 113A4 is extendedfrom the CS bus line 113 by way of another extended portion 113A4′. Inthe edge portion where the extended portion 113A4′ is arranged, nodomain line has been produced. That is why the extended portion 113A4′has a narrow width.

It should be noted that the extended portion 113A3 of the CS bus line113 and the drain extension line 117 overlap each other at their endswith an insulating film (such as a gate insulating film) interposedbetween them, thus forming a storage capacitor CS. Where this storagecapacitor CS is formed, there is a contact hole (not shown) and thesubpixel electrode 111 a is connected to the drain extension line 117.Likewise, parts of the extended portions 113A1, 1113A2, 113A4′ and 113A4of the CS bus line 113 that overlap with the subpixel electrode 111 aalso function as parts of the storage capacitor.

The example shown in FIG. 25 is different from the example shown in FIG.24 in that the CS bus line 113 includes another extended portion 113A5for further shielding the horizontal one CL2 of the central dark lines.The extended portion 113A5 of the CS bus line 113 has been formed so asto connect the extended portions 113A3 and 113A4 together. This extendedportion 113A5 of the CS bus line 113 also contributes to forming astorage capacitor. If the opaque portions are defined by these extendedportions 113A1 through 113A5 of the CS bus line 113 in this manner, thedimensions of the respective extended portions are defined with theinfluence on the capacitance value on the storage capacitor CS takeninto consideration.

In a situation where the central crossed dark lines are all shielded asshown in FIG. 25, even if misalignment has occurred in thephotolithographic process step to define a multi-domain structure, thevariation in the areas of the four liquid crystal domains (see theliquid crystal domains A through D shown in FIG. 1) can be minimized.Specifically, as already described with reference to FIG. 2( a), if thephotomask has misaligned in a photolithographic process step to form amulti-domain structure, then the areas of the liquid crystal domains Athrough D will vary from the predetermined values. In that case, if theopaque portions are provided to shield the crossed dark lines at theboundary between the liquid crystal domains and if the boundary betweenthe liquid crystal domains that has actually been defined as a result ofthe misalignment falls within the width of the opaque portions, then theareas of the portions of the liquid crystal domains A through D thatcontribute to the display operation will not vary from theirpredetermined values. As described above, the areas of the liquidcrystal domains A through D are preferably substantially equalized witheach other to achieve a sufficiently good viewing angle characteristic.

If the opaque portions should be omitted if possible to achieve asufficiently high luminance and if each pixel (or subpixel) has avertically elongated shape, an opaque portion for shielding thehorizontally extending dark line CL2 in the central crossed dark linesis preferably omitted and an opaque portion for shielding the dark lineCL1 extending vertically (i.e., in the longitudinal direction) ispreferably provided as shown in FIG. 24. By providing such a verticallyextending opaque portion, even if the photomask has misaligned, thevariation in viewing angle characteristic can be reduced. This pointwill be described with reference to FIGS. 26( a) through 26(c).

FIGS. 26( a) through 26(c) schematically illustrate elongated pixelswith dimensions of 210 μm>×140 μm. The multi-domain structure thereof isthe four-domain structure with the liquid crystal domains A through Dshown in FIG. 1. In each of FIGS. 26( a) through 26(c), a pixel in aleft-side region (which will be referred to herein as an “L region”) ofthe liquid crystal panel is shown on the left-hand side, while a pixelin a right-side region (which will be referred to herein as an “Rregion”) of the liquid crystal panel is shown on the right-hand side.These drawings schematically illustrate situations where in themanufacturing process of this liquid crystal panel, the right and lefthalves of the liquid crystal panel are irradiated with light separatelyin the photo-alignment treatment due to its huge size, for example, andwhere the photomask has misaligned in the opposite directions eithervertically or horizontally on the right and left halves. In FIGS. 26( a)through 26(c), the dashed lines are boundaries that divide each pixelinto four domains.

In this example, the pixels 10A1 and 10A2 shown in FIG. 26( a) includeonly a vertical opaque portion 21, while the pixels 10B1 and 10B2 shownin FIG. 26( b) include only a horizontal opaque portion 22. The verticaland horizontal opaque portions 21 and 22 both have a width of 5 μm. Andthe pixels 10C1 and 10C2 shown in FIG. 26( c) have no central opaqueportions at all. The magnitude of misalignment is ±5 μm. In theleft-side region, the photomask has misaligned 5 μm rightward and 5 μmupward. On the other hand, in the right-side region, the photomask hasmisaligned 5 μm leftward and 5 μm downward.

The following Table 1 shows the area ratios of the liquid crystaldomains A through D in the respective pixels shown in FIGS. 26( a)through 26(c) (respectively corresponding to a through c in Table 1). Itshould be noted that the area ratios of the respective liquid crystaldomains are shown with the widths of the dark lines CL1 and CL2 nottaken into account and with the area of the pixel minus the area of theportion to be shielded by the opaque portion supposed to be one.

TABLE 1 Area ratios of respective domains A B C D Total aL region 0.24690.2716 0.2293 0.2522 1 aR region 0.2522 0.2293 0.2716 0.2469 1 bL region0.2613 0.2744 0.2265 0.2378 1 bR region 0.2378 0.2265 0.2744 0.2613 1 cLregion 0.2551 0.2806 0.2211 0.2432 1 cR region 0.2432 0.2211 0.28060.2551 1

On the other hand, the following Table 2 shows the ratios of theluminance of the pixel in the right-side region to that of the pixel inthe left-side region when the screen is viewed at a polar angle of 50degrees (i.e., so as to define an angle of 50 degrees with respect to anormal to the display screen) in an azimuthal direction of 0 degrees(i.e., the horizontal direction and three o'clock direction on a clockface) and in an azimuthal direction of 90 degrees (i.e., the verticaldirection and twelve o'clock direction on a clock face). Table 2 alsoshows the increase in the luminance of the pixel in the right-sideregion with respect to that of the pixel in the left-side region.

TABLE 2 R region luminance/L region Increase in luminance of R regionluminance to that of L region Azimuth of 0° Azimuth of 90° Azimuth of 0°Azimuth of 90° a 1.100 0.929 +9.98% −7.13% b 1.050 0.867 +5.00% −13.31%c 1.100 0.867 +9.98% −13.31%

In the example shown in FIG. 26( c) in which no central opaque portionsare provided (corresponding to c in Tables 1 and 2), the difference inluminance between the pixels in the right- and left-side regions isgreater than 10% at the azimuth of 90 degrees. As a result, a seam ofthe light radiated (representing the boundary between the right- andleft-side regions) is visible.

In the example shown in FIG. 26( b) in which only a horizontal opaqueportion is provided (corresponding to b in Tables 1 and 2), thedifference in luminance between the pixels in the right- and left-sideregions is as small as 5% at an azimuth of 0 degrees but is greater than10% at the azimuth of 90 degrees. As a result, a seam of the lightradiated is also perceptible.

On the other hand, in the example shown in FIG. 26( a) in which only avertical opaque portion is provided (corresponding to a in Tables 1 and2), the difference in luminance between the pixels in the right- andleft-side regions is less than 10% at both of the azimuths of 0 degreesand 90 degrees. As a result, a seam of the light radiated is hardlynoticeable.

As a result of a subjective perception test, the present inventorsconfirmed that the seam was hardly perceptible if the difference inluminance between the pixels in the right- and left-side regions waswithin 10%. Thus, by adopting the arrangement shown in FIG. 26( a), theseam of the light radiated can be imperceptible even if the misalignmenthas occurred.

If only portions of the domain lines produced in the vicinity of theedge portions of the pixel electrode and only portions of the centraldark lines in the pixel region need to be shielded, the opaque portionsare preferably provided such that the difference in luminance becomes10% or less under the conditions described above even when misalignmentoccurs as just described with reference to FIG. 26.

In the examples described above, the opaque portions are provided inmost cases to shield the edge portions and the domain lines producednear the edge portions within the pixel region. However, if the pixelaperture ratio should be given a higher priority to strike an adequatebalance between the pixel aperture ratio and the viewing anglecharacteristic, an arrangement for shielding part or all of the domainlines without shielding the edge portions may also be adopted. Forinstance, in the examples shown in FIGS. 20 and 21, not all of the edgeportions and domain lines need to be shielded so that there is anon-shielded region between the extended portion 113E1 of the CS busline 113 or the extended portion 112E1 of the gate bus line 112 and thesource bus line 114. Also, in the examples shown in FIGS. 20 and 21, astructure in which the source bus line 114 (and the gate bus line 112)and the subpixel electrode 111 a overlap each other is adopted toachieve a high aperture ratio. However, if a structure in which thesource bus line 114 (and the gate bus line 112) and the subpixelelectrode 111 a do not overlap each other is adopted, the opaque portionfor shielding the edges of the subpixel electrode 111 a may be omitted.

(Pretilt Angle and Locations of Domain Lines)

The domain lines are produced in the edge portions due to theinconsistent orientations of liquid crystal molecules as alreadydescribed in detail with reference to FIGS. 6 through 9. That is why thelocations of the domain lines and the distances of the domain lines fromthe edges of the pixel electrode also depend on the pretilt angle.

Hereinafter, it will be described with reference to FIGS. 27( a) and27(b) how the locations of the domain lines change according to thepretilt angle. The pixel region 10D shown in FIG. 27( a) includes twosubpixel regions 10Da and 10Db, while the pixel region 10E shown in FIG.27( b) includes two subpixel regions 10Ea and 10Eb. Each of thesesubpixel regions has the four-domain structure consisting of the fourliquid crystal domains A through D shown in FIG. 1. FIGS. 27( a) and27(b) schematically illustrate an opaque portion 23 and the domain linesDL1 through DL4 and the central dark lines CL1 and CL2 that are producedin the two apertures (corresponding to the subpixel regions).Specifically, the pixel region shown in FIG. 27( a) has a liquid crystallayer with a pretilt angle of 87.5 degrees, while the pixel region shownin FIG. 27( b) has a liquid crystal layer with a pretilt angle of 89.0degrees.

As schematically shown in FIG. 27( a), in the pixel region 10D with thepretilt angle of 87.5 degrees, a part of the domain line DL4 is seen inthe subpixel region 10Da and a part of the domain line DL2 is seen inthe subpixel region 10Db.

On the other hand, in the pixel region 10E with the pretilt angle of89.0 degrees as schematically shown in FIG. 27( b), almost all of thedomain line DL4 and parts of the domain lines DL1 and DL3 are seen inthe subpixel region 10Ea, while almost all of the domain line DL2 andparts of the domain lines DL1 and DL3 are seen in the subpixel region10Eb.

As can be seen, as the pretilt angle nears 90 degrees, the locations ofthe domain lines DL1 through DL4 shift inward in the pixel region. Inthat case, if the domain lines DL1 through DL4 were shielded, the pixelaperture ratio would decrease significantly. For that reason, to achievea sufficiently high pixel aperture ratio (luminance), the pretilt angleis preferably decreased.

Nevertheless, the more the pretilt angle is decreased from 90 degrees,the higher the luminance in the black display state (i.e., the lower thequality of the black display) and the lower the contrast ratio. That iswhy the pretilt angle is preferably set so as to strike an adequatebalance between the luminance and the contrast ratio.

FIG. 28 is a graph showing how the transmittance (or luminance) changeswith the pretilt angle, while FIG. 29 is a graph showing how thecontrast ratio changes with the pretilt angle. In these graphs, theordinate is normalized with the value associated with a pretilt angle of89 degrees.

Considering the results shown in FIGS. 28 and 29, a pretilt angle rangein which the luminance and the contrast ratio are both satisfactorywould be from 86.0 degrees through 89.0 degrees.

As described above, the viewing angle characteristic can be improved byproviding opaque portions for shielding at least portions of the domainlines produced in the pixel edge portions and/or at least portions ofthe central dark lines. However, the portions to shield may bedetermined appropriately so as to maintain a harmonious balance betweenthe viewing angle characteristic and the luminance or the contrastratio.

The multi-domain structure applicable to the liquid crystal displaydevice of the present invention is not limited to that specificallydescribed above but may also be any of the multi-domain structures thathave been described with reference to FIGS. 2 through 5. Therefore,opaque portions for shielding at least portions of the domain linesproduced in the edge portions and at least portions of the boundaryareas at the center of the pixel region (or subpixel region) whereliquid crystal domains are adjacent to each other may be formed by usingat least partially at least one line to be selected from the groupconsisting of the gate bus line, source bus line, drain extension line,CS bus line, extended portion of the gate bus line and extended portionof the CS line on the TFT substrate according to the type of themulti-domain structure applied. Also, if necessary, a black matrix (BM)on the counter substrate (i.e., color filter substrate) may be used aswell. The shielding structures could be easily modified or combinedaccording to the type of the specific multi-domain structure in variousmanners other than those specifically described above as embodiments ofthe present invention.

INDUSTRIAL APPLICABILITY

A liquid crystal display device according to the present invention canbe used effectively as a TV monitor or in any other application thatrequires high display quality.

1. A liquid crystal display device comprising: a vertical alignmentliquid crystal layer; a first substrate and a second substrate, whichface each other with the liquid crystal layer interposed between them; afirst electrode, which is arranged on the first substrate so as to facethe liquid crystal layer; a second electrode, which is arranged on thesecond substrate so as to face the liquid crystal layer; and at leastone alignment film, which is arranged in contact with the liquid crystallayer, wherein a pixel region includes a first liquid crystal domain inwhich liquid crystal molecules are tilted in a predetermined firstdirection around the center of a plane, and approximately at the middleof the thickness, of the liquid crystal layer in response to a voltageapplied, and wherein the first liquid crystal domain is located close toat least a part of an edge of the first electrode, the part including afirst edge portion in which an azimuthal direction that is perpendicularto the part and that points toward the inside of the first electrodedefines an angle greater than 90 degrees with respect to the firstdirection, and wherein either the first substrate or the secondsubstrate has an opaque member that includes a first opaque portion forselectively shielding at least a part of the first edge portion fromincoming light, and wherein the pixel region further includes second,third and fourth liquid crystal domains in which liquid crystalmolecules are tilted in second, third and fourth directions,respectively, around the center of the plane, and approximately at themiddle of the thickness, of the liquid crystal layer in response to thevoltage applied, the first, second, third and fourth directions beingdefined such that an angle formed between a two of the four directionsis approximately equal to an integral multiple of 90 degrees, andwherein the second liquid crystal domain is located close to at least apart of another edge of the first electrode, the part including a secondedge portion in which an azimuthal direction that is perpendicular tothe part and that points toward the inside of the first electrodedefines an angle greater than 90 degrees with respect to the seconddirection, and wherein the third liquid crystal domain is located closeto at least a part of still another edge of the first electrode, thepart including a third edge portion in which an azimuthal direction thatis perpendicular to the part and that points toward the inside of thefirst electrode defines an angle greater than 90 degrees with respect tothe third direction, and wherein the fourth liquid crystal domain islocated close to at least a part of yet another edge of the firstelectrode, the part including a fourth edge portion in which anazimuthal direction that is perpendicular to the part and that pointstoward the inside of the first electrode defines an angle greater than90 degrees with respect to the fourth direction, and wherein the opaquemember further includes second, third and fourth opaque portions forselectively shielding at least a part of the second, third and fourthedge portions, respectively, from incoming light, and wherein the first,second, third and fourth liquid crystal domains are arranged such thatthe tilt directions of any two adjacent ones of the liquid crystaldomains define an angle of approximately 90 degrees between them.
 2. Theliquid crystal display device of claim 1, wherein if the horizontaldirection of a display screen has an azimuthal angle of zero degrees,the first, second, third and fourth directions are an approximately 225degree direction, an approximately 315 degree direction, anapproximately 45 degree direction and an approximately 135 degreedirection, respectively, and wherein the first and third edge portionsare parallel to a vertical direction and the second and fourth edgeportions are parallel to the horizontal direction.
 3. The liquid crystaldisplay device of claim 1, wherein if the horizontal direction of adisplay screen has an azimuthal angle of zero degrees, the first,second, third and fourth directions are an approximately 225 degreedirection, an approximately 315 degree direction, an approximately 45degree direction and an approximately 135 degree direction,respectively, and wherein the first and third edge portions are parallelto the horizontal direction and the second and fourth edge portions areparallel to a vertical direction.
 4. The liquid crystal display deviceof claim 1, wherein if the horizontal direction of a display screen hasan azimuthal angle of zero degrees, the first, second, third and fourthdirections are an approximately 225 degree direction, an approximately315 degree direction, an approximately 45 degree direction and anapproximately 135 degree direction, respectively, and wherein each ofthe first, second, third and fourth edge portions includes a first partthat is parallel to the horizontal direction and a second part that isparallel to a vertical direction.
 5. The liquid crystal display deviceof claim 1, wherein the first substrate further includes a TFT, a gatebus line, a source bus line, a drain extension line, and a storagecapacitor line, and wherein one of the first, second, third, fourth,central and another opaque portions is defined by at least a portion ofat least one line selected from the group consisting of the gate busline, the source bus line, the drain extension line, and the storagecapacitor line.
 6. The liquid crystal display device of claim 5, whereinthe at least one line has a portion that is bent or broadened in adirection that crosses its length direction, and wherein the at leastthe portion of the at least one line includes at least a part of thebent or broadened portion.
 7. The liquid crystal display device of claim5, wherein the first substrate further includes a gate bus line extendedportion that branches from the gate bus line, and wherein one of thefirst, second, third and fourth opaque portions includes at least a partof the gate bus line extended portion, and wherein the gate bus lineextended portion includes a part that is opposed to the drain extensionline with an insulating layer interposed between them.
 8. The liquidcrystal display device of claim
 1. wherein the second substrate furtherincludes a black matrix layer, and wherein one of the first, second,third, fourth, central and another opaque portions is defined by aportion of the black matrix layer.
 9. The liquid crystal display deviceof claim 1, further comprising two polarizers, which are arranged so asto face each other with the liquid crystal layer interposed between themand to have their transmission axes crossed at right angles, wherein thefirst, second, third and fourth directions define an angle ofapproximately 45 degrees with respect to the transmission axes of thetwo polarizers.
 10. The liquid crystal display device of claim 1,wherein the vertical alignment liquid crystal layer includes a liquidcrystal material with negative dielectric anisotropy, and wherein the atleast one alignment film includes two alignment films that are arrangedso as to sandwich the liquid crystal layer between them, respectivepretilt directions defined by the two alignment films being differentfrom each other by approximately 90 degrees.
 11. The liquid crystaldisplay device of claim 1, wherein the at least one alignment filmincludes two alignment films that are arranged so as to sandwich theliquid crystal layer between them, and wherein respective pretilt anglesdefined by the two alignment films are substantially equal to eachother.
 12. The liquid crystal display device of claim 1, wherein the atleast one alignment film is a photo-alignment film.